My boyfriend's dog barks at him when he's aggressive with me?? [I Need Advice]

My boyfriend and I live together. He had a dog before about a year before I started dating him.

Tank (the dog) has never had a problem with me. He's the sweetest. One thing I've noticed is if my boyfriend plays aggressively with me like picks me up or wrestles me Tank barks at him until he stops. He doesn't like when my boyfriend gets rowdy with me.

If I play aggressively with my boyfriend, Tank doesn't bark at me though. The other day he playfully was smacking my thigh and Tank barked and got in his face. I playfully punched my boyfriend's arm a few times and no reaction out of his dog. Any thoughts??

I thought it's because I'm female and small and Tank knows I can't hurt him.