That's a fair criticism. Doing research on real is tough -- everyone's experience is a little different, and is colored by their personal history -- and it'd be wildly unethical to put test subjects through an in-person experience stressful enough to induce lasting PTSD. Some studies, like the Tetris intervention one I linked elsewhere [1], used real trauma patients; others, like this one, have to rely on stress simulants like a violent film.
I will note, however, that Irréversible [2] -- the film this study used excerpts from -- is exceptionally violent. It's not a run-of-the-mill action film. One of the scenes the study probably used graphically depicts a man being beaten to death with a fire extinguisher.
[1]: https://www.psych.ox.ac.uk/news/tetris-used-to-prevent-post-...
I guess maybe the core of my confusion comes with the term "intrusive" or "involuntary" memory. To me, in reference to PTSD, this sounds extremely negative. But perhaps you were in a situation where you saw someone die, perhaps even someone you know, should the goal be to only think about these things in therapy or when you sit down to meditate? Is involuntary/intrusive thoughts on these bad so long as it doesnt have major effects on your stability?
Not nearly as traumatic - but when I went through my last break-up I thought about it non-stop for a few weeks. I was able to get through my work and keep up social engagements fine, but otherwise it consumed me. Would it have been better to only think about the situation in therapy sessions and allotted meditation time? Maybe? But I'm not that sure on that I probably needed a few weeks of internal "involuntary" struggle in order to be free of the negative thoughts around it going forward.
I guess for me the answer is that if your brain is thinking about something, even if it seems a bit disorganized, you are still processing it on your own time and the short term benefits of not thinking about it then may not actually be good for your long term. Though perhaps this runs counter to established literature I'm not aware of.
It seems plausible to that thinking (even if involuntary) about any other traumatic memory may result in short term stress but in the long run help you process it and be healthy? Like in my own experience thinking about something a lot on my own is part of therapy - since I really think about how I explain the situation and what really happened - so I guess I'm skeptical that not thinking of something is actually good for mental health in the long run even if in the short run it works.