I suppose not. But then why did not the FF, in their specific and infinite wisdom simply include the actual word "free"?
I find it important to remember that not all the FFs were for slavery and that slavery was a compromise that wasn't meant to stand the test of time.
I also did not post on this thread to debate this issue, but to give points of reference (Dred Scott and Fredrick Douglass) to the OP who can take note as s/he wishes.
Had you read the REST of the article, you would have found this sentence:
The Founders pointedly avoided using the term slaves, for fear that would legitimize the institution.
To specify "free" would have done no less to give tacit approval to slavery.