That quote has nothing to do with Sally Hemings case. Do your research before accepting everything you read on the Internet.
On top of that, Hemings-Jefferson scandal is far from a settled.
Read this (Executive summary of the Jefferson-Hemings Scholars Commission ):
After a careful review of all of the evidence, the commission agrees unanimously that the allegation is by no means proven; and we find it regrettable that public confusion about the 1998 DNA testing and other evidence has misled many people.
The Monticelo foundation has admitted it. It is enough to me.