This is the feedback I got from GOG's tech support. Assuming the underwear being permanent during exploration were accurate (it doesn't explain why a female V can be topless during exploration), the gray polygons issue was not even considered.
Except its not normal underwear, indeed if you turn on the filter, you have 2 types of underwear ontop of each other.
Instead you get this weird big boxer type underwear, its like a debug version of the character model in that sense, this cant be right.
Now if its the underwear with the filter on that you can kinda see, which looks more like a string, at least that looks more natural.
The F are they doing at CDPR.. this better be someone from tech support who didnt really read the question.
edit : i forgot, it can clearly be forced to show what it should be if you rapidly change pants, so that answer from tech support simply cant be right.