Another producer (I can't remember who, or what show they were talking about, maybe it actually had to do with Star Trek) complained about the arbitrary standard of allowing women's outfits that were very low-cut on top, but the censors would go into conniptions of you tried to show the lower portion of a woman's breasts at all.
That's mentioned on the same page of The Making of Star Trek that I quoted earlier. Whitfield quipped "Perhaps the censors are afraid moss grows there." (It was probably mentioned elsewhere too.)