Nice, I laughed out loud when reading that question.

I guess it depends on where they are exactly on the asexual spectrum, or even on the aromantic or aplatonic spectrums, because there are many ways to experience sexuality differently than allosexuals.

For example, some autistic people may be masking solely to try to fit in with neurotypicals, while others are trying to fight themselves, to force themselves to become neurotypical, so yearnposting could either be to force yourself to be sexually active or just to appear more normal. I have heard of both of those situations with aces.

Or it could be a manifestation of sexual desire, as in being horny, even though someone is not feeling sexual attraction, as in wanting to do something sexual with someone in particular. And you can replace "sexual" with "romantic", "sensual" or "platonic", because you could either have or pretend to have romantic, sensual or platonic desire. And there are many other variants and microlabels, so there are many other possibilities.

I myself just yearn for girls on fedi because I am starved for affection and because fedi tends to appreciate those posts lol