The AoE spells are in a weird place because they're neither better-on-three versions of F1/B1, nor better-on-three versions of F3/B3. They kind of have the Potency stats of the former but the speed/cost stats of the latter. Maybe if they also enjoyed reduced cast times or MP costs when you already had three stacks of their associated elemental aspect?
I'm guessing the team wants to avoid giving Flare a bunch of fiddly, conditional modifiers, and I'm sympathetic, because it makes the spell feel less special if it's so weak as to not be worth casting unless you do a lot of prep. I prefer the model in which it's great by default but the consequences of HAVING cast it are awkward and inconvenient (at least until you accrue some higher-level traits).