I have seen people get VA disability (service connected) for a hysterectomy and sexually transmitted diseases.
He needs to keep applying. The DAV (Disabled Vets of America) will help him for free, and they are very effective at getting the VA system to work right.
The VA resists this kind of disability ruling because it opens the floodgates for thousands more vets who had similar injuries. It took many years for the VA to surrender on the thousands of Agent Orange cases. My friend got cancer from exposure to it.
I bet going on his local tv news station’s consumer help segments and naming his congressman would oil some squeaky wheels real fast.