As far as I know, the FAA has no access to military medical records and I'm sure I would have heard. Also they are not going to read every pilot/service member's record and cross-check with your FAA medical history...far too much effort. The disability thing was low-hanging fruit...if somebody had a disability claim and an FAA medical at the same time there was a good chance of funny business, and the disability record told them exactly what they were looking for in one glance.

If you're not flying at all it's irrelevant, you are effectively "self grounded", which gets you off the hook until your next medical, or resumption of flying.

The only situation which requires specific timely notification of the FAA in all circumstances is DUI-type issues.