I don't have proof that its a female thing, its just what I have read on a few different sites they say females tend to hang upside down more and be a little more acrobatic, but I had never seen any of mine do it till recently.
Mine do it alot during thier shower and when they come out of the nest box They'll hang off the front or the perch and just stretch thier wings for a few mins. before comming out all the way (come to think of it most of the time when they do it comming out of the nest box it's mostly the females doing it)
It's cute when they do that. Both mine do it ALL the time. One is always upside down when you look over at them. They both hang upside down off the perches, the cage sides and the swing. Chiclet goes all the way around the perch part of the swing. I think its entertaining..lol