I'm running an all wizard game that has five submerged level wizards in it and they have found that they really like their maneuver spells. And, yes, this is the way that I have interpreted the rule and have been running it. Though, in this case with a wirlwind air spell, I would say that the targets would use might to resist. Against a zone type force effect like a whirlwind, you are either strong enough to stand it or you're getting thrown around. I would maybe make an exception to this if a player tagged a scene aspect that was appropriate, like "Stacked Crates" that might provide cover that they could dive behind.
Also, the way I have been playing this is that the caster does not automatically know what the resisting level of each target is. I make them take a calculated risk as to how many shifts they think they will need. They could make an assessment, of course if it makes sense. In this case, if the caster of the whirlwind had either observed the target using his might before or had directly contested them with might, they might get a good idea of how strong the target is.
Hope that helps.