I think at that age he doesn't know what his sexual identity really is and it more likely to be a passing phase.
I hate to be disagreeable, but I KNEW by the time I was 10 that I really liked boys. It was young and I had no inkling of any attraction towards a girl. There have been times in my life where I had a crush on a girl, but they were more emotional and not sexual. (Does that make sense?) But I never considered myself bisexual for having a crush on a female. I guess some might. Andi