some of the people working at these companies have admitted that they fudge data for well known people.
Usually to upset them
Some of it may be deliberate gaslighting—I saved a link to a story titled DNA Testing Companies Like 23andme Admit Adding Fake African Ancestry To White Profiles In Order To “Screw With Racists”, but it has since been scrubbed from the Internet.
But this link below about identical siblings getting different test results from different testing companies speaks to basic human incompetence:
Investigation Puts Ancestry DNA Kits To The Test Among Sets Of Triplets