> The death of the Buddha’s mother, Māyā, when giving birth to him serves no purpose as myth, and can therefore be accepted as fact

That seems dubious. One potential purpose is convenience--one less person in the picture. Another is a deliberate excise of a female character, reflecting either a fear or simple apathy toward the feminine. The Cult of the Virgin Mary in Christianity is an example of what can happen if you leave the door open for a potentially powerful feminine character.