Before it occurs it can also be directed, either partially or completely, by both the specific content introduced by the GM and the (perhaps metagame) manner in which this is done; and that's where part of the issue lies.I don't want to go too far down this rabbithole - but if player input hasn't occurred yet then it can't be nullified. Nor can it be modified. It can be instigated.
I've never run DL-1 but a similar module-mandated use of Force might be the transition in the Slavers series from A-3 to A-4: the party have to be captured come what may. (great series but that one bit of it that never felt right somehow)This is what I've been focusing on ... around the DL dragon armies case - there are some different analyses going on, and probably more posts I haven't read yet, but my take is that this is not a modification or nullification of player input but nevertheless is force because it guides/manipulates towards an outcome.