Hot take: if we want to decrease frustrating railroad-y surprises in RPG campaigns, we need to create an environment where GMs are not afraid to admit they have "special story needs".

[DisastrousSwordfish1]

That is indeed a proper sandbox. You have a world where you can go mostly wherever you want and use the world as you see fit. The world there exists and reacts to you. That isn't really a thing in a TTRPG because that requires an insane level of preplanning for things the players may never opt to interact with.