Should a Purple Heart be authorized long after an injury if the service member refused evacuation and treatment was never documented?

Should a 79 year old Vietnam combat veteran be authorized a Purple Heart and the benefits that go along with it, some 50 years later? Injured, he refused to be medevacked and stayed with his artillery unit to keep it operational while supporting the 101st AB on Don Ap Bai (Hamburger Hill) after being knocked down and hit by incoming mortar shrapnel. 17 others were medevacked out, for some similar issues and his medic died two days later on a hospital ship from the incident. Subject has 5 or 6 stiches in his arm which were done quickly in the field by the Battalion Surgeon, and a split thumb that was wrapped and never stitched as others needed more pressing medical attention. Other minor shrapnel was pulled put of their bodies by their peers without much incident. The internal welt and scar tissue in his thumb had been bothering him for years, so recently the VA x-rayed it, find nothing there other than some excessive internal scare tissue inside creating some numbness and minor pain. They plan to surgically remove it and stitch it up properly to re-heal properly. From the x-rays they accidently discovered another 7mm piece of shrapnel still imbedded in his palm ("radial aspect of the third metacarpal") of his same hand, not an issue according to veteran, since he never even knew it was still there. Someone at the VA told him he should apply for a Purple Heart. He tried, and was told that minor issues do not qualify and must be assessed at an official aid station within a reasonable amount of time of the incident, and not just in the field by some medic (Fred Paddleford, he's on The Wall).