You're just wrong about this.
With the Taurus Demon fight the intention to having that break in the wall is for the boss to be able to knock you off the arena. It's meant to punish your bad positioning and teach you not to stand near ledges when fighting something bigger than you because taking a big hit with your shield up still knocks you backward.
The Taurus demon wasn't even originally supposed to be the boss fight on that bridge in DS1, he was repurposed to that area, and they just never bothered to fix his movement to not fall off the map because the development of DS1 was rushed and the game was never finished. (I can't find the source for this information. I remember it from an old Zullie The Witch video, but given that she has hundreds of videos about the various technical changes in all of the Souls games I don't really have time to look for it at the moment, so just "trust me bro.")
The clip for the Dark Souls 2 boss that I posted, the Dragon Rider is even worse. If you ever play it, it is very clear from the arena and boss design that it's all designed for the boss to knock YOU off. There's levers you can find and pull in the area leading up to the boss fight that cause the arena to get larger so that you have less of a chance of getting knocked off. The intention is that taking the time to explore the area would help alleviate a disadvantage later in the boss fight. It actually ends up doing the opposite because the bad boss pathing means that having the smaller arena makes it easy for him to accidentally kill himself.
There's a bunch of other places in all of the souls games where enemies just ledge themselves and die because their pathing is bad.