As a trans person in a trans friend group, this is fucking hilarious. Trans people tend to have more casual views on sex and relationships, and often don't care for, or at least are okay eschewing, monogamy. If you're willing to question the gender systems that society forces on everyone then you're willing to question other things. No group of trans women is spontaneously having an orgy (unless that was the plan going in), its hyperbole for the joke, poking fun at the tendency for trans friend groups to all have been sexual partners at some point.
All the trans girls being modest and saying they arnt cute, but then complimenting all the other girls calling them cute which give euphoria and turn on.