Right, but sadly AMD Ryzen Pro aren't sold directly to consumers (well unless you buy grey market on ebay), even if they did there's no such thing as a Ryzen Pro motherboard, or a Ryzen Pro BIOS. Not to mention AMD has been slow to upstream various EDAC related kernel patches.
It's not really a supported config, there's no guarantee it will work, no promise from AMD (other than it's not disabled), and you can't return a Ryzen CPU because the ECC doesn't work.
Various tests from various reddit posts show that some vendors "qualify" ECC dimms as working (an inserted Dimm increases ram available), some correct bits but don't correctly tell the kernel, and others actually do correct and report. So it's basically just a big mess. I'd buy an Epyc, but sadly unlike Intel the premium for a "server" chip is huge, if you can find them anywhere near MSRP. I looked for a Epyc 7313p near MRSP (announced in March 2021) without luck and finally gave up and bought a Ryzen.
With all that said, ASRock is from what I can tell the best AMD motherboard company to support ECC with AMD. I've got a ASRock X570D4U, other than it refusing to allow sharing a IPMI/BMC interface with the system, I'm pretty happy with it.