No, I checked it again, and he is DEFINATLY hitting Yoshi, not pointing. This may be to get a certain automatic response (i.e., sticking the tongue out) from Yoshi.... But there are 2 reasons I think this:
1. Notice the forward motion of Mario's arm. It is not a bent, pointing motion, but more of a striaght forward, hitting motion.
2. If you look at Mario's hand, there is no finger extended to point with. It is simply a closed fist.
There you have it.
You know what? I got really, really bored one day so I decided to change my signature.