Haven't seen anyone ever include Mario Party Amiibo in with a "wave", ever.
Wave has always referred to the Super Smash Amiibo, as they are the only ones being released in "waves". I'm not seeing any confusion in the slightest, but to each there own. Maybe someone else could articulate it all better than I am...
Super Mario is getting additional waves, don't kid yourself.
As for Europe, they staggered the release pattern there so the fans have been calling the initial releases wave a, and the later release wave b. Some Americans have been doing the same with calling the initial 3 (sheik/bowser/toon link) wave A.
Fan nomenclature != manufacturing nomenclature.