I think you have hit on something. Another possibility is that he or his minions have submitted so many forged documents to various review entities that they’re getting scared of the legal consequences of submitting a real document.
Hawaii accepted birth registrations from third parties, practically on hearsay, at the time of his birth, and it’s possible that if there is an actual certificate, it records the fact that it was filed by his grandmother. But still, that leads,to the question of why - and where he was really born. (I’m voting for British Columbia, personally.)