Another advantage radial AoEs have over conal is the lack of necessity for a target. In a jumbled mass of enemies, tabbing to the right enemy to maximize the usefulness of the conal can be difficult, especially if enemies keep dying and you need to keep re-targeting and adjusting your position. With a radial AoE, one just plants as close to the middle as they can and blasts away.

In this way, I was surprised that Tenka Goken wasn't likewise upgraded to be radial as well as Fuko, so I guess my brain kind of ran the opposite direction that yours did here.