This is very interesting to me as both a history major and an attorney. Slaves were not considered persons from a legal standpoint, so Heinegg's representation seemed plausible to me, and would be consistent with them not being listed like those people considered to be persons in a census.
If you have been following the thread, you may recall that there is a Rhoda Pierce who was a Mulatto whom I am evaluating as possibly being my 3GGmother. Rather than being legally married in Beaufort County to a freed slave, Jacob Grist, Rhoda was considered to be a common law wife and cohabitating with him until his emancipation. Their names appear in a long list of similarly situated people in a register: https://familysearch.org/pal:/MM9.3.1/TH-1-14707-56520-16?cc...
My other Beaufort County relatives who appeared as people in a census prior to 1870 had their marriages documented in the same marriage registers/bonds lists as the Whites. Perhaps this practice varied from county to county, or perhaps the slaves' marriages were not recognized by the state until emancipation. Either way, it is good for me to be aware.
I wish I could find civil procedure books for the county courts in Washington and Beaufort; perhaps I could find out more about my 2GGpa and his parents. Thanks very much for the input. I will be very cautious in determining freed status going forward.