No, this is still wrong.
When the dice are rolled, the GM could decide that there's a cook, or no cook, whether or not the roll is a success or failure. Because as I and others have pointed out, there are many options here. The GM could decide there's a cook in the kitchen. If the roll is a success, there's a cook, but the cook is turned away and doesn't notice the PC enter. If the roll is a failure, the cook notices and screams. But that doesn't mean the cook only exists once the players enter the room! If the players look through a window or listen at the door, the GM will say that they see/hear a cook, unless there is a very good reason for them not to. And then the PCs can adjust their plans accordingly. If they go through and succeed, the cook would still not notice them, and if they fail, the cook would notice them.
(Remember, that example with the cook was from one blog post, and wasn't the best example possible.)
If the state of the fiction is decided before hand, then the GM has to hope that they've accounted for everything the players are going to do--which means there's a good chance that the GM is going to have to improv anyway. The GM may have carefully plotted out the existence and location of every single member of the household so they know who will be around when the players break in, only to have the players brazenly knock on the door, maybe in an illusory disguise. Oops. Did the GM think to flesh out everyone's personalities as well and decide how they'd react to such an event? Or the PCs could go a completely different route. I mentioned a zillion posts ago about how I was in a game that expected us to go on an interdimensional bank heist to get a certain artifact, and instead we hired a lawyer. Or the PCs could just fireball the place.
Which goes back to what I have said repeatedly. You will have to improvise (or else stop the game while you figure things out, or worse, railroad the PCs or forbid them from taking certain actions), and your game isn't worse off for the improv. And I'd bet that you wouldn't end the session thinking "that wasn't good because I didn't plan everything out ahead of time."