The Importance of Spontaneity in Collaboration

I'm curious, and especially in the context of a game, I mean, Sam is probably just very atypical. But so much has to be so planned that the world of mockups and all that become quite essential. So how do you even reconcile the need for this sort of spontaneity knowing that the final product is going to have a certain amount of indeterminacy? It's like an AI where it will do things of its own accord once you've set it loose, but you've also set the outer parameters in which it can operate.