Formally that firework PTSD exist, but not in the form described. I know Soviet Afgan veteran dude and a girl fleed from Donbass in 2017, what they have is kind of muscular instinct without any mental side effects. They start of loud blasts or thunderstrikes, but treat this more with a humour or just ignore. Funny that Afgan veteran is one who always bring fireworks for any celebrations/parties to "let's make noise and blast them all for the fuck sake!".

So, effect definitely exists, but I don't see any real harm to mentality at least for people I know. They are absolutely normal people despite more noticeable reaction to sudden loud noises. Their basic instinct we all have just more developed, but humans are humans because they could conscionely control their reaction to that instinct. And who the fuck never gave a start when lightning sudenly strike nearby?

I think you have to be already fundamentally mentally unstable to get something like PTSD described by MSM.