rock pikmin
i mean richter has one difference, why not make it for this one too?
Rock Pikmin requires a new model, animation, and physics...Holy Water being Aura Damage instead of Flame Damage is an easy change..even changing Chrom's Up Special to be Ike's with slight differences is easier then giving Alph Rock Pikmin just to make him a little different enough to be an Echo Fighter instead of an Alternate Costume.
Not to mention, every single one of Olimar's animations still works fine for Alph, this wouldn't be the case for most of the other Echo Fighters that have more distinct differences in their personalities and styles then Olimar and Alph do.
In games where there's not a lot of voice acting, that is fine. Plus he does talk, but only in text so far...
Even in Super Mario Sunshine, a game that did have a lot of voice acting, Yoshi still only said 'Yoshi'.
Also, while not a main game, Super Mario RPG had given Yoshi a unique way of talking, talking like this (Hi, Mario!), which highly implied that he wasn't speaking like Peach, Bowser, Toad, etc talked but rather Mario was just able to understand him..yet for some reason needed Yoshi to be an interepter for the other Yoshies..which implied that he was still saying just 'Yoshi'..or the sound effect equivalent used from Super Mario World to Mario Kart 64..
Funnily enough, Yoshies only being able to say 'Yoshi' even predates Yoshi's Story, being how the Yoshi's talked in Super Mario Adventures, a comic/manga that was in Nintendo Power Magazine between January & December in 1992 before being released on its own in 1993 as a Nintendo Power Catalog order (though I found my copy at a Wal-Mart in 1996) and recently in 2016.
As such, if Illumination features Yoshi and has him just say 'Yoshi' over and over again, its not their fault but rather Nintendo's for making it fairly clearly that Yoshi can only say 'Yoshi' and make other non-descript noises.