>>43408465Ho-Oh also didn't star in a movie
Initially, the only legendaries in Gen 2 were Ho-Oh and the beasts. Lugia didn't exist until Takeshi Shudo (the director of the anime at the time) asked Game Freak to design a Pokemon to star in the second movie. So they made Lugia for that and put it in the game afterwards.
Had Lugia been conceived by Game Freak alone to be Ho-Oh's counterpart, it probably would have been Water to contrast Ho-Oh's Fire. But since they were conceived separately, Lugia's type didn't have to "match" Ho-Oh's
