Sadly I have seen both, a man wearing a "wife beater" type tank top and a man wearing what I would believe to be a bathing suit in the MDR. These were on different cruises and both times they remained there for the whole meal so it seems those are "allowed" no matter what is in writing.
On my last visit to Palo for brunch I saw 3 women in shorts, 1 in yoga/stretch pants, and 1 wearing a concert type tshirt.

Meanwhile a man in nice khaki, below the knee shorts and a short sleeve button up shirt got sent back to change. He looked MUCH nicer than some of those women, so figure that one.