Limebloods having fire powers was very very very likely written for Hiveswap 11+ years ago while Homestuck was still in progress (seeing as foreshadowing for it exists in Hiveswap/earliest Hiveswap concepts), so that is not retroactive at all.

On the other hand, this whole thing spawned from a poll for what funny celebration drawing Hussie would do for the server, so when everyone voted on "we need lore and designs for these offscreen implied characters from the joke planet which is about disappointing fans with lame versions of characters they like!", yes, the only outcome possible is stupid retroactive shit made up later.