Isn't the lesson here not to rely on any one source of diagnosis?

There have always been differing medical opinions, so allowing patients to cheaply sample many in order to rapidly get to the end is better than having a one off rarely in practise used test because it's prohibitively expensive.

The FDA are simply enforcing the medical industry monopoly on diagnosis. You can expect any potentially disruptive effort along these lines to also mysteriously fail to ever be approved.