Pretty sure a "Finishing" Move in that context means the climax of the dance, not actually finishing your opponent... That would be why Finishing Moves don't typically translate directly into damage. 'Finale Belt' would be more appropriate under that logic.
This is a very nice belt for casting Hysteric Barrage. It may have 2 less accuracy when compared to a Potent Belt, but STR+3 from Potent does not modify HB's damage; it's modified on DEX.