That makes sense really. 2 possible body parts to hit, each with there own hit box and animations.
I watched a youtube video by a dude named thatguyoverthere, and he has a similar process to creating his bosses where instead of animated artwise, they are animated thru code and each part is its own active object. I dont have a link, but its def. worth a look. I found it by searching mmf2 tutorial.