Which were left to his daughter in his will. Yet you claim Lee owned none.
However the family owned four others under his wife's name, although Grant himself was responsible for supervising them.
For the sake of this argument let's assume that is true. What you are saying is that Lee's wife inherits close to 200 slaves but Lee doesn't own them. Grant's wife is given several slaves by her father and all of a sudden they belong to Grant?
In reality, Grant's wife had the use of four slaves. Title to the slaves do not appear to have been passed on to Julia Grant, much less her husband. The Dent family slaves were, according to Julia Dent Grant's autobiography, freed shortly after the Emancipation Proclamation. There is reason to believe that this was a bit of an exaggeration on Julia Grant's part. Evidence indicates that the Dent family slaves just ran off over time after the Emancipation Proclamation, and that includes the slaves that Julia Grant had use of. In any case there are no accounts of any slaves accompanying Mrs. Grant on her visits to her husband or on any of her other travels after early 1863.
The difference is the Lee family had no interest in owning slaves and freed all the ones they inherited once the debts were paid off. The Grants, however, had no such scruples and didn’t free theirs until they were forced to by the 13th amendment, or else their slaves ran away before that as you say they might have done.