Artistic Oversight here or......? (EW Spoilers)

[Lersayil]

I think its establieshed that the forms of Blasphemies come from the (collective?) minds of transforming individuals. Some of the ones in role quests take on very specific forms related to myth or recent events. It wouldn't be weird if some Allagan specimens remained engraved in mythology (Garuda).

That said, yeah, it probably has a good amount to do with cost saving. It does make for a convenient excuse though, and they can play around with the idea of recurring motifs in history.