I never finished YIDS, but that sounds like something Nintendo would do.
All I know is that Yoshi, THE Yoshi, is supposed to be a consistent single person in Super Mario 64 DS, the spin-offs, supposedly the one with his own text box in Super Mario World, supposedly the one with whom Mario can speak in super Mario RPG, etc. No Yoshi in Yoshi's Island stands out more than any other, though one of the green ones in Mario & Luigi: Partners in Time ought to be Yoshi...