Well, what's the alternative? The length at least is descriptive, there's no question about what it does. Double negatives are unfortunate, but that all depends on what the default value previously was (in the event that there actually was no flag like this, it definitely makes sense to make the default false, and then the language follows).
But sure, maybe PreventApply... would've been better. Then again, PreventApply... sounds weird, and should probably be PreventApplying..., but, ehh, naming is hard.