It is something I know for a fact since I worked at 23andMe for 4+ years. Looks like the first responder already found the relevant section and posted it. It's not an ironclad assurance, and there are a few caveats, but these provisions, together with any scrutiny an attempted acquisition would bring (the database is big and well-known enough where it's virtually guaranteed), can provide peace of mind for some. There are certainly risks and I don't advocate that everyone gets tested without considering them, but "insurance company buys 23andMe, gets all the data, and starts discriminating based on it", is a very low-probability event based on what I know.
It says that I would have to pay 9 dollars a month. Do you know if I can tell them to charge the whole subscription once instead of 9 dollars every month?