I'm less saying "it definitely isn't" and more trying to show the complexity of understanding this and the paucity of evidence. Is long-term stress different from a one-off traumatic incident? How much stress does trauma cause? Is therapy effective at preventing stress caused by trauma? What part of therapy is effective: can you stick someone in a room with a nice doctor and no therapeutic plan and achieve a result? Does therapy make things worse for some patients? Which patients are those, and how do you tell?
My personal opinion is that trauma probably has an effect, it's a lot worse in sustained cases, many of the symptoms are mixed up with other conditions, treatment for it is effective (in that it hits statistical significance) but not particularly effective (in that the effect size is small), treating healthy people can make them worse, some traumatised patients probably also get worse after treatment, and the symptoms of e.g. ASR/CSR are so vague that some of them apply to most of the people who read them.
My personal opinion is that trauma probably has an effect, it's a lot worse in sustained cases, many of the symptoms are mixed up with other conditions, treatment for it is effective (in that it hits statistical significance) but not particularly effective (in that the effect size is small), treating healthy people can make them worse, some traumatised patients probably also get worse after treatment, and the symptoms of e.g. ASR/CSR are so vague that some of them apply to most of the people who read them.