The bigger thing to me is that i think the “where your ancestors came from” feature is a scam. I think that;s just the hook to sell people on it.
“came from”
I read the white paper on that subject for one of the testing companies. They basically run correlation against a database of “known” people. Those self identifying as being native to a country to include parents and grandparents.
So your surmise is correct - there is no national genetic marker, e.g. a french-gene. It’s pretty much racial and when checking out their own work, they admit in the white paper that the best results are quite regional, such as northern vs southern europe.
The most interesting thing they found was that it was notoriously difficult to find correlation for french and german areas. The belief is that that is due to that region being somewhat of a mixing bowl for europe.
So the ancestral dna bit is cute, but not really that useful. You’ll get better info doing your own genealogical research.