This sounds like something one girl at your college made up and it caught on just recently.
It's not so surprising. Women in college are still really naive and are just exploring sex, so they're curious and that's why they talk about it all the time. They're also full of hormones and horny, too, so they're both inexperienced and obsessed. It's the age when women talk about sex and penises the most, because they're exploring and curious. That behavior can look like sexual experience, from the perspective of someone the same age I'm sure, but from my perspective as a much more mature woman, it's obvious that it's all just bravado for the attention. They're acting in a naive and innocent way, because they're compensating by behaving in an overly crude way (just like men do around the same age!) Whenever a guy claims that "all women" talk about penis size, that means that he's in high school or college, because that's the only time when most women will do that. That behavior usually stops after they graduate and move into the next phase of their lives.
Just realize that those girls are really ignorant and their judgments are meaningless right now. They really don't know what they're talking about, so don't let anything they say about sex or penis size or stupid "tests" like that affect you. They're still figuring it all out, just like the guys are.