You are equating false negatives to harmful information, when in reality it is the same as simply not taking the 23andMe test. The only thing 23andme enables you to do is act sooner on things they get right, and any false negatives are irrelevant—you didn't ask for a diagnosis and they aren't claiming to give you a diagnosis. You cannot be harmed by a false negative any more than you will be harmed by not buying a 23andMe kit.
> you might decide against certain treatments or tests based on that
Since you are mentioning treatments means, you must misunderstand what the purpose of the test is for. If you have current medical problems that you need treatment for, you wouldn't use 23andMe's statistics in order to chose a treatment, you ask your physician to help you get the treatment you need. If 23andMe had a false negative on my condition instead of the true positive, I would still get diagnosed once I started developing symptoms eventually. Nobody who starts having health problems thinks "I should first consult my 23andMe results for things that I should specifically mention to my physician that I don't have".
> you might decide against certain treatments or tests based on that
Since you are mentioning treatments means, you must misunderstand what the purpose of the test is for. If you have current medical problems that you need treatment for, you wouldn't use 23andMe's statistics in order to chose a treatment, you ask your physician to help you get the treatment you need. If 23andMe had a false negative on my condition instead of the true positive, I would still get diagnosed once I started developing symptoms eventually. Nobody who starts having health problems thinks "I should first consult my 23andMe results for things that I should specifically mention to my physician that I don't have".