My thoughts are encapsulated in a twitch streamer's tweet below:
That's just not accurate though. Blind implies you are going in blind, meanwhile you can look up stuff about the game, even read a guide or a walkthrough, and if you've never played the game before it'd still count as a first playthrough, but it'd not qualify as a blind one.
The point of a blind playthrough in the context of a stream is that you get to see the gamer first experience something and their genuine, original reaction to this information. If you've read spoilers or seen others play through a game it may still be your playthrough but that aspect of discovery and the reaction to this discovery would not be the same.
I kinda feel like I'm having to explain 2+2 = 4 here, is everyone an alien who doesn't understand why people care for blind playthroughs and is just being overly literal and basing their opinions on things they read instead of having authentic first hand knowledge here?