I've always wondered about that too. I use a long heavy hawk that is good for cutting brush, driving stakes and splitting small wood. It is a lot heavier than anything anyone else uses but it works for me.
Basically, whatever you get used to will work for you. It just makes sense to me to carry a working hawk instead of a special throwing hawk. The throwing belt knife that I use is extra long, not because I wanted a longer knife, but because it throws from about the same spot as the hawk.
Your hawk and knife need to work together so you don't have to spend too much time remembering where to stand.
I have found that a hammer poll hawk with a narrow ground edge will stick in a real hard block better than one with a standard axe grind.
Many Klatch