Yeah, AWS is the only exception I've encountered :)
But if you have backup second factors (you have backup second factors, right?) and you're worried about Passkey lock-in for whatever reason… just use that other second factor for AWS or any other account which supports only one.
But if you have backup second factors (you have backup second factors, right?) and you're worried about Passkey lock-in for whatever reason… just use that other second factor for AWS or any other account which supports only one.