Pre-approval just before surgery?

So I have a bcbs plan and I need corrective jaw surgery. The issue is that in order to prepare for jaw surgery I need to be in braces that will intentionally make my bite worse for jaw surgery to then align everything together.

I already paid to be put in braces but ortho is now afraid to mess up my bite as needed because my insurance will only give pre approval just 90 days before surgery. Ortho keeps asking me if I can talk to anyone from insurance and I just dont know what to say or do. Its not like they can just say yeah sure we’ll cover it?

I had no idea my insurance worked like this as many cases I’ve followed of people who get jaw surgery (who obviously have a different insurance than mine) are able to get pre approval before starting braces so they have some reassurance. I cant find anything online about when insurance can give pre-approval. I would preferably like to chose a plan in the future that would allow me to get pre-approval before starting braces so I don’t waste my money again.