Crimson Longinus
Legend
I just said the literal opposite of that. So...
Similarly, improv can be directly in line with the player's choice, if the GM is improving answers that align to that choice and input. If the GM has the idea of "ogre" and then just inserts it regardless of choice, we have Force. If the GM is improving in ways that really don't consider the player's choices, at best we're in a strange middle place, but quite often we're in Force territory because the GM is still selecting an outcome that doesn't care what the players actually did.
By your definition any improvisation that is not informed by player choices is force, or at least middle ground close to force. Considering that GM has to improvise a crap ton of stuff than cannot reasonably be directly derived from player choices, that's a lot of force.
Like seriously, the GM describes a door. PCs, without any particular expectations decide to open the door. What are the possible methods for the GM to determine what's behind the door, and which of these are force? Preplan it specifically for every door the PCs might see? Randomise? Make it up on the spot? Decide beforehand that first door the PCs open has thing X behind it? Have couple of vague ideas of things that could be behind doors, and put what feels appropriate for the mood of the table at the moment there? And most importantly: why does it matter?