This is a joke right? No one refers to people as "melanated POC", do they?
I actually got in spat with a coworker once at a previous company for politely and sincerely asking what one of these neologisms meant (latinx in that case).
Melanated just means dark-skinned, in case you’re indeed being sincere. And yes, there are people who talk like this.
I can guess what it means, but it sounds like a pastiche and an exaggeration from far right activists that are trying to portray leftists as being out of touch.
OP's point is it's an affectation, aimed at signalling to an in-group. It's not a common phrase. Like "folx" or "foid", the jargon/cant is there to exclude "normies". Even an appeal for help comes with a barbed "... but not from YOU, outsider" meaning.