Sorry, just too many fairy tales.
When I visited, they had wood huts where the slaves lived.
Written source material, archeological evidence. IIRC, Monticello is privately owned and operated. The NPS, for better or worse, has nothing to do with it. We were there a couple of years ago, booked one of the in depth tours. It was very good, thorough, detailed. We were actually surprised at the lack of PC.
The article stated that the location was described by Jefferson’s grandson. Thomas Jefferson Randolph had a part in settling the $100,000 debt that was outstanding when his grandfather died.
Funny; I remember brick rooms painted white, and attached to the lower level of the main house, near the kitchens and with doors on the side of the vast gardens.