As other people have pointed out, this reasoning is inconsistent with other character choices in the game. Charizard can barely fly even though he's a Flying type, for fuck's sake.
Why on Earth are we ignoring the battles in Prime and Prime 3? Meta Ridley's not a different character and his body shape is the same. In Prime 1 Ridley is able to fight well after his wings burn off and in Prime 3 he spends most of the fight grounded.
because I've not played Prime and Prime 3