This remind me of a cat's primordial pouch which is the fluffy part of the kitty belly that humans like to rub (and may or may not be a trap), and extra-pervy cat enthusiasts get addicted to huffing (see CAT HUFFING). It's not a secondary sexual characteristic. Both sexes have it, and it seems to have evolved to assist faster running according to felinologists.
And yes, when hairless (say if a cat overgroomed its nethers) they definitely look NSFW when they dangle during standing and walking.