I'm a little confused..? (a little TMI)

So my guy and I were fooling around the other day and well he did something he's never done before. I'm pretty flat chested so I'm not sure why he would do this. But he would run his penis in between my breasts.. I didn't really mind him doing this but I was just confused because I feel like this move would've worked better with someone who has a larger chest (which I do not). But he seemed to enjoy it.. Opinions, thoughts, concerns?