Not to split hairs but do we know this for a fact? He clearly doesn't want infants but I don't think he's worried about whether or not they've had experiences...
It's not about whether they have had experiences. It's about whether they've been through puberty or not. As people have said, R Kelly is in actuality an ephebophile. There are a lot of men who are not pedophiles, (in fact, men who are disgusted at the idea of pedophilia) that have ephebophilia. That's where you get sayings like "If there's grass on the field, play ball." and those leering grown motherfukkers who start paying attention to a girl once she hits around high school age.
But socially, people have got it into their heads that a pedophile is a grown person who fukks with anyone under 18 (even though the age of consent is lower in many states; because it's 18 in California and that's where we get a lot of our media from, that's why we make that judgment call).
That being said, I don't condone R Kelly's actions, but I think we should differentiate between a grown person fukking with teenagers and a grown person who would molest a 5-year-old.