html5 does not even allow any other values in <meta charset=>. I think you need to use a different doctype to get what the screenshot shows.
Another funny thing here is that they say “but not limited to” (the listed encodings), but then say “must not support other encodings” (than the listed ones).
> the encodings defined in Encoding, including, but not limited to
where "Encoding" refers to https://encoding.spec.whatwg.org (probably that should be a link.) So it just means "the other spec defines at least these, but maybe others too." (e.g. EUC-JP is included in Encoding but not listed in HTML.)