The idea that a femboy and anyone they fucked would be too taboo to create a myth about is beyond absurd.
This has nothing to do with taboo. Zeus turning into a bull and abducting Europa isn't there so that a couple Cretan furries can feel represented, it's an affirmation of the conquering male - a core value of contemporary human culture.
This is a general problem with From worldbulding. They write those stories in the guise of societal allegory, but there is no society behind them. Their ontology is confused, stuck between the Lovecraftian inhuman unknowable, and nebulous human sacral experience devoid of any of its natural practicality. It exists in the service of Miyazaki's end of days fetish, rather than trying to appear is if it could have ever been the standing order of things that involved more than just the pantheon alone.
When you remove the human component of the abstract/human dynamic of myth, the audiance will naturally try to humanize the abstract. This, in turn, makes stories like Miquella and Mogh lose al pretense of a higher meaning, and circle back to base physicallity.