Good point. I remember reading that a lot of freed blacks were often in worse condition than slaves because not only did they have to provide their own necessities for themselves, they also were surrounded by people refusing to accept their status. Having a name like Freeman could have been a way to avoid that, or could have been a kind of "fuck you" to those refusing to accept their status as free men.
Of course it's not like every freed black was better off than every slave, but some slave masters were nice to their slaves, and some freed blacks were impoverished and were not protected under the status of being useful property.