The only misleading part of this is "must employ...standard HTTP methods to assert state on resources". REST does not require using HTTP -- in fact, your own first link states, as its first rule, "A REST API should not be dependent on any single communication protocol".

Its true that whatever protocol(s) it uses should be used in standard (not resource-specific) way, but there is no requirement that HTTP be the only protocol, or one of the protocols, used.