>>12405468I agree with you that the base stats should/could just be swapped around, however if they produce split evo's for pawniard or bisharp gamefreak then has to give each one of them a different method of evolution, wheras if it's just a forme change they only need to add one method. And hey why not make them gimmicky? I mean they're gonna be based on chess pieces so there's probably some gimmick potential.
tl;dr Base stat total stays the same for Bisharp alt. formes and gamefreak makes them formes cause it's slightly easier. Also, gimmick potential.