I think you're being argumentative for the sake of making arguments.

For starters, your very first point (if I died 40 years later) is explicitly addressed in my post above yours. I told you that in medicine survival from trauma is defined as a hospital discharge. If the question is "did you survive" in your scenario then the answer is "no" but if the question is "did you survive your trauma" then the answer is "yes."

I understand your question about patients who die from complications of trauma remotely, but that is not how traumatic deaths are statistically defined. I mean, do you believe that everyone who died of a heart attack should be classified as having died from a genetic condition, since they were predisposed to heart disease? Should every lung cancer be classified as a poisoning because it is related to inhaled toxins? No. If you died of "complications of burns" - whatever that's supposed to include - but this was remote from the trauma, then you did not die from the trauma, you died from whatever that complication was.

What if there were no hospitals

Are there really any countries that build 12 story apartment buildings but have no hospitals?

if he refused admission and died weeks later

For starters, somebody with 90% burns and no treatment would die minutes to hours later, not weeks later. But even if that were the case, he would not have been discharged from a hospital, thus not meeting the criteria for survival, thus being classified as a traumatic death. I'm still failing to see where the difficulty is: there is a definition from traumatic mortality, that this patient, even in an absurd scenario as described by yourself, still would clearly fit into. Either he died or didn't, and this happened either with or without discharge from hospital. There is no gray area - one of each of those two variables occurred and thus this death/survival would clearly and easily be classified.

I suppose that to satisfy your questions, a practical definition should be that the patient is "dischargeable" from hospital - meaning obviously, that if they presented to hospital they would be discharged home with or without outpatient management. This settles the question of "what if I sprain my ankle, don't go to hospital, and die years later - I wasn't discharged so is that a trauma death?" The answer would still be "no" because you would not be admitted to hospital for that injury, so even if you'd come to hospital you'd be discharged. Common sense is much easier to use than ultra-specific definition though.