AMD will sell you an Epyc AM4/AM5 CPU with the same specs at the same MSRP for most of their Zen4/Zen5 chips (not the APUs and I think there may be a couple missing skus on the Epyc side).

I doubt there's much of a meaningful difference other than a jumper for the brand. Retail pricing and availability might differ.

Nothing wrong with Ryzen for a server, you can get AM5 server boards from Asrock and they support ECC. If you need more they make AM5 Epyc CPUs that are just Ryzen parts with Epyc written on the box and IHS

Just out of curiosity why not?