Would the US ambassador to France really be all that free from prying eyes? Sally Hemmings was 14 when she went to Paris and 16 when she left. Maybe Jefferson waited until she was older.
I agree that there's no ironclad proof the children were Jefferson's, but people may have gotten tired of picking this or that one of your other relatives and putting all the blame on him so as to spare Jefferson the embarrassment of illegitimate children.
When it turned out that the neither of the Carr brothers was the father of Sally's children, people were reluctant to go on playing the same game, to pick out some other relative who hadn't previously been a suspect just to preserve Jefferson's reputation.
Jefferson's brother was the likely father.
When he was older, much older than most men are catting around. The point is that the DNA evidence shows that the father of at least some of her children was a Jefferson. But, neither the DNA evidence or the documents that survive resolve the issue.
You can chose whatever version you wish to believe, but some Liberal historian at Monticello who has a political agenda that motivates her conclusions is not the final word. I will give her credit for convincing most people to believe her story in spite of her version is, at best, one of the several viable explanations.
Any it turns out, Sally Hemmings offspring, at least some of them, are my cousins and I'm fine with that.