Sounds like the Sony camera bug of several years ago : in that case it was iirc the disabling of the camera's IR filter (usually only done when used with IR illumination) in daylight.
https://www.youtube.com/watch?v=CpWBIt2gjzY
OnePlus has announced plans to disable the colour filter camera on its latest OnePlus 8 Pro flagship blower after it emerged the device could see through plastics and clothes under certain conditions. In a (Google-translated) post to its Weibo page, the Chinese smartphone giant acknowledged the issue and apologised, saying: " …
.. what this "color filter camera" was, here's a description. Seems to me like not a great deal is being lost by disabling it. I'm surprised that the (intended) effects can't be reasonably well duplicated with the regular camera and some software, but what do I know.
So far I've seen nothing approaching NSFW demoz of this "flaw", just males in black t-shirts with something solid underneath. Given the internet, I assume the lack of bra or nipple photos means that this is no more effective than x-ray specs.
True pervs will still need a readily available but expensive IR camera. Note that this is the same technology that is or will be used for mass body temperature screening.
The same effect could be seen on 35mm film camera pictures. Nothing to do with the camera sensitivity - just the freeze effect of a shutter. When you look at someone wearing clothes the eye is scanning and forms an aggregate picture. A fast shutter camera shot sees from just one instant angle - and you can therefore effectively see through pores in the material. Possibly the same effect - but more pronounced - that you get when white material is wet.
Kiniki make close-fitting swimsuits out of a material that is full of tiny perforations - such that it allows 80% of the sunlight through for tanning. Together with a camouflage pattern the costume looks solid when worn. Hold it up to the light and you can see all the holes. Not sure what a fast shutter camera would see.