I'm not entirely sure, I mean, from my level of understanding it could all be relatively faked data and I wouldn't know any different. They claim they do quality review[0] and you can compare them to some of the competition[1], and they don't offer anything except genealogy records and your results in a big file you can download. You can use that information to parse on other sites for medical things (there's quite a few sites that take the data file as an upload, actually). I'd be interested in reading a more comprehensive audit though.
[0] - https://customercare.23andme.com/hc/en-us/articles/202904760...
[1] - http://www.isogg.org/wiki/Autosomal_DNA_testing_comparison_c...