By the war's initiation, Lee was managing his estate's slaves (i.e. including delaying the terms of their emancipation, deciding their personal futures, and occasionally having them disciplined or even whipped, etc.). No one said he owned any of them but it didn't make a whit of difference to those slaves at the time.I agree the letter really isn't news. We do need a source to show "his" slaves were whipped for disobedience, however. They we're his father-in-laws, not his, if we're talking of the same bunch.
It's such a small point but an oft-repeated irritant; employed in the attempt to try and soften that the primary tenant of Secession and the Confederacy was slavery. It goes like this: "because Lee didn't own any slaves it means that for him the war wasn't about slavery." Edited.