First, force isn't exactly the same as railroad, in the sense that while a railroad requires force not all instances of force are railroading.I'd just add that the GM isn't unilateral in that though. He has the players implicit consent to use the authority they have given him to produce framing and consequences that lead back to the adventure path when the players decide to unknowingly do things not involving the adventure path.
Is it really force/railroad if the GM is giving the players what they agreed to at the start of the game that they wanted?
To me that detail makes all the difference in the world.
Second, if the GM is doing the things that define force, it's force. This is why even some of the people who have strong preferences for minimal/no force in the games they run/play have been clear that force isn't in itself bad. In any example that involves the people at the table agreeing to play through a given adventure/adventure path, the use of force is kinda expected. What makes it bad, best I can tell, is if/when a GM is doing it and pretending they aren't.