Maybe if we still called it “Shell Shock” instead of PTSD, people would get the help they need.
It's not necessarily the same thing. They had it right in WWI to associate the condition with the artillery shelling troops often endured but it took the advent of the MRI to confirm it.
Trenches might have shielded WWI soldiers from shrapnel but the blast of an explosion can travel around corners and down into the trench you're in. So even though the shrapnel didn't get you, you still got your bell rung. And repeatedly getting your brain knocked around inside your skull can cause chronic traumatic encephalopathy. What they were describing as "shell shock" in WWI now is recognized as having been CTE.
MRIs of young men who've served in the GWOT and been exposed to (and survived) multiple IED blasts show that CTE is often accompanied by brain stem atrophy. Brain stem atrophy can interrupt the Hypothalamic–pituitary–gonadal axis, which causes secondary hypogonadism. Hypogonadism (low testosterone) can cause listlessness, loss of sexual appetite, depression, and even cowardice.
PTSD, on the other hand, often has no organic cause. However, it does share many symptoms with CTE and "shell shock," but they're not the same condition.