Perhaps it’s not related to gender and is perhaps related to some other reason

The image provided in comments shows its a beach so maybe its to prevent hypothermia ?

How exactly would wearing a bikini top prevent hypothermia?

I realize you’re not a gamer, but I have a “frost guard cuirass of the wintery north” on my female elf, it’s basically a bikini made of dry ice, but it gives +83 to cold resistance.