I remember a Flex from the '80's where Franco Columbu was insisting that pec work would atrohy a women's breasts. I read that in maybe '93 when I was 10 and of course believed every word. (hey if Franco says it....) I decided to never do a bench press as long as I lived. The horse*** W6 referred to I believe is more often than not popularized by "expert" pro BB doing their "as told to" articles in mags.
A personal anecdote for what its worth, which isnt much. I started lifting 9 months ago at age 19 years 8 months. I was a full C, nearly D. My 1RM bench was a shaky 85lbs. I did 135lbs last saturday with nice control, minimum back arch. I'm still a C. Personally I kinda wish it did shrink the boobs.