I first read about women on the pill choosing the "wrong men" in an article about compatibility in the magazine, Psychology Today. In a nutshell: part of our attraction is how the opposite sex smells. We are more attracted to people with a different smell than our own because they have a different genetic make up, the better to produce strong offspring. Theoretically, the pill affects women's sense of smell, so they choose a mate whose smell would normally (subconsciously) turn them off. I don't have the article around me, but I distincly remember the author citing how many women, who divorce after getting off the pill, say, "I can't stand the way he smells!"
As for the tshirt test: if the tshirt were worn by a man with similar genetic make up, she would reject it: i.e. "This reminds me of my dad!" A woman doesn't wanna marry a guy who smells like her dad or brother. If the tshirt were worn by a guy with a different genetic make up, she would either like the smell or least not be turned off by it.
