Remember that Sheik was the persona of OoT Zelda which is a different Zelda than the TP Zelda. Because TP Zelda got a Sheik transformation that was exclusive to OoT Zelda it is a canon break. But those are just the small examples every Smash Character has a canon break, but technically Smash Bros is just an Otaku playing with his Nintendo figurines in some crossover fanfic, so maybe he could just buy a relatively smaller Ridley trophy.
Anyway, having a smaller Ridley would just be a more noticeable adaptation compared to the rest of the cast. Has anyone noticed the Green Charizard in Smash? Heck even in Brawl Ridley's transfomation to Meta Ridley was out of canon. There was a different storyline behind that.
Also the Mario example is a different canon to main series Mario, but then again Mario doesn't need to make sense because at one moment he could be breathing in space and the next moment he could be made out of paper.