They did this with ECC too?! I chose AMD for my new computer precisely because of its ECC memory support!

That's extremely scummy. I'm going to reconsider.

With laptop ECC, which is admittedly a very niche thing. I believe ECC on desktop Zen 4 does work but I’ve heard reports that it took about a year of BIOS updates before it became stable. (Zen 4 was the first generation that shipped a DDR5 controller so that is, if not reasonable, at least understandable.) Looking at Zen 5 specs on the AMD website now, there too ECC is supposed to be available all the way down to the Ryzen 9600.