Any time you have to refer to yet outside definitions, you’re in trouble. “persons bound” or “unfree persons” did not just include slaves. It included indentured servants.
Nice try though. It’s amazing the lengths to which neoconfederates will go to defend slavery in the CSA which, by the way, DID use the term slavery, and which Alexander Stephens said was the purpose of forming the CSA-—to ensure the permanence of slavery.
But it included slaves. That's the point.
The USA Constitution - the one Lincoln twice swore to defend - mentioned slavery THREE times. Or more accurately, it provided for slavery.
How did that happen?
Like this: the states of New York, New Hampshire, New Jersey, Massachusetts, Rhode Island, Connecticut, Pennsylvania, Delaware, and Maryland voted to include slavery in the USA Constitution. Oh yes, let's don't forget that Virginia, North and South Carolina, and Georgia also voted to include slavery in the USA Constitution.
In defense of northern sensibilities, only 9 of the 13 states that voted for slavery were in the north.