Its a curse response to the Vaporeon or Pokemon compatibility copypasta that often circulates within the community.
Why the fuck do those copypastas talk about "compatibility?" like bruh, i ain't sticking my dick in a fantastical wild animal because i want to be compatible with it. i want our parts to be different enough that can feel the species barrier on my shaft. if it feels like it was built for humans then it's clearly not an imaginative enough choice. i want the puffy spade of a mightyena in heat at least. i want to fuck the flower of a venusaur like a horny beedrill on a pollinating spree. i want a collaborative blowjob from the same mega mawile. i want to watch a mienshao to literally bend over backwards like a broken lawnchair to give herself a rimjob while i'm hitting that from behind. what i don't want is to be bored to death by the bog standard gardevoirs and other shit that 'seems so fit for humans.' i'm not gonna halfass my crimes against nature, when i fuck a wild fantastical beast, i want it to feel like i'm fucking a wild fantastical beast.