I *do* think it's pheromones...

What you have to realise is that everyone reacts different to the pheromones of everyone else - a phenomenon already studied, albeit not enough yet, imho, with comparisons between same-gender and opposite-gender attracted people. There is nothing impossible or even unusual in the possibility that some people are far more attracted to the pheromones emitted by an adolescent or a prepubescent than those of an older person. So yes, you could be particularly attuned to the pheromones of teen girls.

In that respect, I will never stop mentioning the story of Y, who was my lgf in 2005, when she was 10. If you look at pics of her, she is attractive, but you could certainly find other girls just as attractive "visually" without too much effort. But she had such pheromones!!! Many times, I was at some place and she arrived; and before I saw her because I was looking away from where she arrived, and before I heard her because she might have been silent and not speaking so I didn't hear her voice or steps... I felt her arriving. And it regularly caused certain body parts to swell before I even saw or heard her. It is impossible to explain other than through pheromones.

Admittedly, she's the only girl with whom that's ever happened... Otoh, I have read mentioned here, and it constantly happens to me too, that people are randomly going about their own business, and suddenly something tells them to turn their sight to some place, and there she is, a pretty lg!!! I suppose at least part of that might be your sight learning to tell a girl far faster than other objects or your ear catching lg voices far more than other sounds; but I am sure pheromones play a part too...