I think you're running into some sticky issues by overformalizing some of what's going on.
First things first: when an insurance company 'denies coverage' for something, that thing then becomes 'uncovered'. The 'denial of coverage' is the thing that decides whether something is 'covered' or 'uncovered'!!
With that settled, it might be easier to think of 'denying coverage' and 'uncovered' as the same thing as 'prohibiting'/'prohibited'. While technically, those aren't the same, in the world of our health care system, they may as well be - and it will help you see what's actually happening here.
So, the conclusion is saying that when the insurance company prohibits lab tests, medical care suffers.
(A) is saying that the physical exams + the now-prohibited tests together provide a better diagnosis. I.e., that the now-prohibited lab tests add value.
Now, this is NOT saying that the lab tests add value when they are prohibited. That just doesn't make any sense. It's saying, essentially 'those tests that are now prohibited? Yeah those? They are actually really useful when we do them.' It's simply pointing to the lab tests the insurance companies deny coverage for, and then telling us that when they are actually performed they add value to diagnoses.