The difference here is that even though CT scans might be useless, at least the pictures themselves are accurate. Whereas 23andme told me that my ancestry was a mix of Nigerian, Japanese, and Iranian. Then suddenly two years later they decided I was 99.9% white. No explanation given, they didn't even send me an email, I just showed up one day and found out that I was a different race, and suddenly the genetic risks of what I was supposed to be worrying about were completely different.