I am not surprised.
Paradoxes of wartime: while my father was minesweeping in the Bristol Channel, not exactly a luxury cruise but a very gentle introduction to war, my mother was putting out incendiaries in North London.
After a successful haul of mines, the crews would get together with rifles and shoot them. The object wasn’t to set them off (though this did happen) but to sink them so the mechanisms would fail. The worst part of the job, apparently, was coaling (in which the officers had to join).
As a result, I’m quite supportive of the idea that PTSD is caused or worsened by brain damage due to pressure waves etc., and is probably worse with modern munitions. Despite the big bangs in the Bristol Channel, and the even bigger bangs during the invasion of France and attack on Japan, neither my father nor his friends got PTSD or any particular fear of fireworks.