Nope. Prep is situation, not outcome. If I prep room A and room B, though doors A and B, respectively, and the players select room A, then it's not Force to present room A as the outcome. This is directly in line with player choice -- they choose door A and get the associated answer. Force would be applied if you were going to room Z no matter which door you selected -- this is disregarding the player choice -- ie, it doesn't matter what choice the players make, they get the same answer.
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.
And, again, this isn't necessarily bad. In fact, whether it's bad or not will entirely depend on the table. Lots of tables are perfectly fine with a good bit of Force -- a skilled GM can wield Force in quite entertaining ways after all. Some tables will be very unhappy with even a little or any Force. I can't tell you if a given instance is bad or not, outside of my personal opinion. I can analyze the structure of the play and say if it's Force or not, outside of the rather thin grey area along the line (Force doesn't really have a large sloppy area of maybe).