I never noticed it until I was watching the X-2 credits. The guy that did Braskas voice did a lot of them in x-2 (the two ronso kids, and lots of other NPCs)

I think I was watching it because I was like 'man, wakka sounds a lot stupider than he did' But it woudln't make sense to change voice actors.

incidentally I thought kimarhi sounded a lot different too. I guess a couple of years does that to someone.