I have a Ryzen 5 1600 with a pair of Crucial ECC UDIM. It works perfectly on the ASUS Prime B350M-A/CSM uATX board. Stress tested. Errors are logged and halt behavior is confirmed (ubuntu 17.04).
Though perhaps the rare frequency of cosmic ray flips makes that acceptable.
When systems rebooted with less memory than the system configuration database said they should have most of the time there would be a multi-bit error detection, machine check, and 'memory update' in the IPMI buffer.
BTW, I'm hoping that ECC is there.