This matches my relative's experience. He only got help with PTSD once he was given the green light to retire from 20 years in TS clearance job. It's pretty frustrating, once you see how dramatically their life improves following a few months of seeing a psychologist. He could've gotten that help a decade ago.
Furthermore, your relative is a grown adult who decided that he should stay the course and not see a therapist for his condition based on possible consequences on his career. Clearly this happens in every career where there are high rewards, in this case a life time pension(valued over $1mm). Well, shit guess what, he made to him what seems like the best choice.
For reference, look at a surgeon who is getting the shakes on his right hand or the NFL player hiding his broken collarbone injury during his free agent try outs. Or for a more military reference: the young guy hiding his fracture on X bone during selection phase for Y job. (doctor's typical question: "why didnt you come to us sooner when you knew something was wrong", clearly has no idea the drive and motivation behind the young man)
Note that for this to be OK, we should expect to see the same number of incidences in the military as one expects to see in civilians.
If we have a reason to expect lower suicide rates from military personnel (e.g. better health, less incidents of alcoholism/substance abuse, no joblessness, regular psychiatric evaluations, etc compared to the general population), then it's not OK.