Great article, you've identified and addressed an issue with PnP RPGs that I've been argueing with people about for close to 20 years now, and did so far more articulatly than I have been able to.
Simply put I think the theory of GMing your quoting from the DMG II (which I don't have) has been a rising problem since "White Wolf" started encouraging that kind of GMing back in the early days. Truthfully I can see why that advice exists because it is far easier to fudge things/railroad/script encounters than GM seriously. It's also much easier to write modules and adventures that move from plot point to plot point rather than encouraging free form exploration and player creativity/planning/strategy. I tend to look at modules like "The Isle Of Dread" (which is similar to what you were talking about with your maps) as being pinnacle of adventure design even now, while deceptively simple, I think they have done the job better and in a more satisfying fashion than a lot of what I've seen produced nowadays.
One piece of advice I tend to give most GMs, and try to practice myself, is to have more than one adventure ready to go just in case the unexpected strikes. That way if the wrench gets thrown into the proverbial gearworks, you aren't stuck trying to ham handedly fix things, can let the chips fall where they may, and simply start the next adventure.
I will also go so far as to say that the most memorable things for me have always been when things have not gone as planned (both as a player and GM). This has included things like the party falling for a deception and leaving an adventure early, thinking they finished it when they didn't (think of Acerak's "false tomb" in the original Tomb Of Horrors), or one case where I played in the worlds (accidently) shortest Ravenloft adventure... the GM was running some variation of Castle Ravenloft, and using a bunch of house rules for critical hits and such... as well as some gothic horror trappings like saying that Holy Water is like Napalm to the forces of evil and lights on fire when it hits them (as an incentive to get us to be careful with it). During one early encounter we were in this church and had Strahd in person(unknown to us) screwing with us from in hiding. Despite warnings and attempts to be careful we wound up lighting the church on fire by using Holy Water. As we were evacuating however a Paladin who had this legendary quality intelligent Holy Avenger with undead slaying abillities and god knows what else happened to find a secret door with an undead behind it. Given the character's girdle of giant strength he decided to be a smart arse and instead of opening the door or whatever said "I slam by sword through it to impale the undead on the other side". He rolled a massive crit which was defined as a "heart impalement" for quadruple damage on the GM's table, combined with some fancy undead slaying stuff. Given that the item in question was defined as a minor artifact one Strahd Von Zarovich died instantly, pretty much losing all hit hit points in one blow and suffering enough additional slaying junk to blast him out of existance. ICly the party never realized why everyone suddenly collapsed into mist (including the burning church), all we knew was we arrived at our next adventure... but well... it was worth some epic chuckles for a while (high level campaign needless to say). The point of this rant is that it's things like that (and including the opposite when they go bad) that are unexpected and can't be scripted that make gaming fun. Had something like that been glossed over, fudged, scripted, or whatever else in either direction it simply would not have been half as entertaining especially seeing as none of the players saw it coming.
Simply put I think the theory of GMing your quoting from the DMG II (which I don't have) has been a rising problem since "White Wolf" started encouraging that kind of GMing back in the early days. Truthfully I can see why that advice exists because it is far easier to fudge things/railroad/script encounters than GM seriously. It's also much easier to write modules and adventures that move from plot point to plot point rather than encouraging free form exploration and player creativity/planning/strategy. I tend to look at modules like "The Isle Of Dread" (which is similar to what you were talking about with your maps) as being pinnacle of adventure design even now, while deceptively simple, I think they have done the job better and in a more satisfying fashion than a lot of what I've seen produced nowadays.
One piece of advice I tend to give most GMs, and try to practice myself, is to have more than one adventure ready to go just in case the unexpected strikes. That way if the wrench gets thrown into the proverbial gearworks, you aren't stuck trying to ham handedly fix things, can let the chips fall where they may, and simply start the next adventure.
I will also go so far as to say that the most memorable things for me have always been when things have not gone as planned (both as a player and GM). This has included things like the party falling for a deception and leaving an adventure early, thinking they finished it when they didn't (think of Acerak's "false tomb" in the original Tomb Of Horrors), or one case where I played in the worlds (accidently) shortest Ravenloft adventure... the GM was running some variation of Castle Ravenloft, and using a bunch of house rules for critical hits and such... as well as some gothic horror trappings like saying that Holy Water is like Napalm to the forces of evil and lights on fire when it hits them (as an incentive to get us to be careful with it). During one early encounter we were in this church and had Strahd in person(unknown to us) screwing with us from in hiding. Despite warnings and attempts to be careful we wound up lighting the church on fire by using Holy Water. As we were evacuating however a Paladin who had this legendary quality intelligent Holy Avenger with undead slaying abillities and god knows what else happened to find a secret door with an undead behind it. Given the character's girdle of giant strength he decided to be a smart arse and instead of opening the door or whatever said "I slam by sword through it to impale the undead on the other side". He rolled a massive crit which was defined as a "heart impalement" for quadruple damage on the GM's table, combined with some fancy undead slaying stuff. Given that the item in question was defined as a minor artifact one Strahd Von Zarovich died instantly, pretty much losing all hit hit points in one blow and suffering enough additional slaying junk to blast him out of existance. ICly the party never realized why everyone suddenly collapsed into mist (including the burning church), all we knew was we arrived at our next adventure... but well... it was worth some epic chuckles for a while (high level campaign needless to say). The point of this rant is that it's things like that (and including the opposite when they go bad) that are unexpected and can't be scripted that make gaming fun. Had something like that been glossed over, fudged, scripted, or whatever else in either direction it simply would not have been half as entertaining especially seeing as none of the players saw it coming.