They have a policy of allowing men into the women's changing rooms to try on women's underwear.
They know what the men do in the changing room, while wearing/ using the underwear and that the underwear is put back on the display for unsuspecting women to find.
Most shops don’t let you take underwear into the changing rooms as you’re not allowed to try them on, so I find this hard to believe.
If I have underwear in my hand they hold onto it whilst I try my other items on.
I think it’s probably just a rumour that does the rounds on SM.
A bit like when they say HIV positive people are injecting blood into oranges.