AFAIK, there is no public beta program for visionOS. It's not even listed on Apple's beta program page.You could wait for public beta, which is downgradable.
You need a developer account to get the beta, though it doesn't cost anything for a basic account. I wonder if Apple did it this way because there's apparently no way to downgrade without the $300 Developer Strap. I've read that some Apple Stores will do this for you, but I suspect Apple wants to limit these requests.