Genki Sudo also makes common use of the spinning backfist. I've also seen it applied at a live KOTC event by a heavyweight.
No it's not a joke. Especially if you know how to throw it.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto