Parmandur
Book-Friend, he/him
Yeah, I still don't see how anyone could think the players know anything about what is coming ahead of time.I doubt that a single person out there thinks that the entire session is read from a script with them memorizing every line - what people mean by "scripted" is all of the plot points are planned out beforehand (generally always true in any DnD game with a remotely prepared DM) and that all the players are aware of the upcoming plot points so that they can "improvise" cool reactions to what the DM throws at them (this part would be unusual of a standard DnD game, and would make it not really be "playing DnD" in my opinion).
It definitely looks scripted if you only watch highlight clips where they only show the epic couple minutes out of a dozen hour livestream, but the video above does a good job of explaining this by just law of averages. If you play DnD for hundreds of hours, some really cool improvised stuff is going to happen even without professional actors being involved. Plus the moments are probably somewhat scripted from the DM's perspective, just as they would be in any normal DnD game with a prepared DM
Certainly Mercer preps well...but the players really, really don't.