[whatwg] Why is the replacement encoding called "replacement" and not "x-replacement"?

[Peter Occil]

Why is the replacement encoding called "replacement" and not "x-replacement"?

As far as I can tell there is no character set or alias called "replacement" in the IANA character
sets list, so accordingly, the replacement encoding should begin with "x-", as in
"x-user-defined", also in the Encoding standard.