What if SOME PTSD is more physical than psychological.
The are a number of mental conditions that have more than one cause. Brain is a complex system and one disturbs it in one place or another and at the surface it all looks the same. Computers are similar - one place it goes wrong and the screen it looks like BSOD.
There is a real value of finding one clear physical cause->effect opening targeted opportunities for treatment and prevention.
But then there are plenty of people with PTSD that have not been anywhere near a blast. It may be one piece of a huge puzzle.