Not all war PTSD is caused from "shells". So to use his logic, unless your flashbacks and hyper awareness (oops those are newfangled psychological terms, guess they have to be dumbed down right?) are caused by the use of mortar shells, then any other use of that term is disingenuous, right?
His argument was that the term PTSD is euphemistic. Not that terms should be hyperaccurate. Shell shock recalls weapons amd war while PTSD calls to mind vague "trauma". It's a term that is a step away from what it actually is.