I almost always stop listening and go into the "Fuck you, your doing it wrong!" mode when I read/hear the "bla, bla, desensitized up to 15min after, bla bla" tests (Yes, I do continue to read/listen after that, so no "you aren't paying attention" comment please).
If I scare you and your pulse is high for up to 5 minutes afterwards, that don't mean that you will suffer a permanent, elevated pulse if I scare you multiple times.
If you think so, please start suing the scary movie business now.
It's an exaggeration, but the point remain the same. A biological response to outside stimuli doesn't result in a f*n "Permanency"-spell so that the subject will continue to experience it without stimuli.
When you watch a fight, a P.O.V shot from the edge of a high cliff, physical pain or other sights that you would react with aggression or panic (fight or flight), your brain is wired to react to it. But you don't actually F*N run from the theater or punch your TV! It's because a healthy brain will dull down the instinct because it realizes that this isn't real.
So you might have an reaction, but it doesn't mean anything more than that your brain and nerves are working.