So, my children were challenging me to name Pokemon today and as I was doing my best (their standards are very high!!), my husband blurts out "Ambassador Seaweed." After I got done laughing so hard that I fell over, he then hits me with "So...when he says his own name, is it Byakuya doing a funny voice, or does he just say it in Byakuya's regular voice?" I replied that of course it's in Byakuya's regular voice, Byakuya would never do a funny voice.
Now, in the Halloween episode, Wakame Ambassador is very much played by Byakuya's voice actor, but they're also Doing A Bit based on the Renji-Byakuya fight. Then I remembered that the Ambassador also appears in BBS, and based on this video, he does very much just seem to just have Byakuya's voice.