My father had pleural plaques. Followed serving on subs in the RN during the forties. Doctors were initially reluctant to tell him what exactly the thickening on his lungs was.

Breathing got progressively worse over a 5 year period, and he ended up on Oxygen, so I can't really see the argument from insurers (although I suppose you can't blame them for trying). The illness still has a major effect, even if it doesn't manifest into anything further.