Emerikol
Legend
I think precious is the wrong word. Maybe defensive of their role as GM?Yup, sure. but I find dyed in the wool D&D and OSR GMs are more likely to be precious about their perceived role and authority. That's not a criticism either, as much as sounds like one, as those GMs have had to forge their style from nothing because the games they play don't provide any of the mechanical support or direction that PbtA game do. A lot of those GMs tend to look at, say, Dungeon World, and immediately get upset at what they perceive to be a ton of constraints on how they run their game. In my experience though, the Keeper moves in good PbtA games tend to encompass pretty much anything a good D&D DM is doing anyway, it just takes some time and experience to realize it.
In my games, I've always held the GM to be the final authority on everything. Of course I am also aware that this phrase is true "Whatever the DM says goes but if he says enough stupid stuff, the players will go too". I also hold that character sensory input from the DM is the only real connection to the campaign setting the players have. I very much tend to follow the rules to publicly change them ahead of the game but in a session, the players can't know enough in many cases to make a case the rules aren't being followed.
One of my quotes is "Are you going to believe the established theory laid down by various scholars or are you going to believe your own eyes?"
So to the degree the players as their characters know the rules, it is knowledge held to be generally true across the land. It's what scholars have figured out over the years and it's pretty reliable but it's not infallible.
For example, if I in the real world came upon a rock that was just floating in the air, I would be quite surprised to see it. I understand gravity should pull the rock down. I would not dismiss gravity as nonsense at that point. I also would not dismiss the fact I have a floating rock right in front of me. Perhaps, I'd immediately begin to try and figure out what other scientific factor is affect that rock. In a world of magic, most people even smart people would be far more open minded about what is possible.