It's an interesting concept.
I might not understand it well enough on cursory googling.
I'll take a shot at my thoughts.
Betrayal trauma is one sort of moral injury we suffer. I am not trying to apologize for cheaters, but certainly in cultures where cheating is *even more normalized* the trauma is not as severe. Perhaps because the violation of the moral code isn't as deep.
I think it is a great term to use to describe what I have called "the loss of something integrity adjacent". Not leaving when you would have previously said you would leave if presented as a hypothetical. The moral injury not just of being betrayed but of being put in a situation where your actions and preferences are contrary to your previously held moral beliefs. This is a moral injury not suffered by those who leave after betrayal.
I do think this is one of the hardest parts of R and I have posted about it a number of times. Shifting your moral code is definitely psychologically painful and difficult to do. Standing up a new moral framework is what is necessary for repair. And I think that is true of the regular betrayal trauma bit as well.
You need to stand up a new framework for trust in a relationship and how you will respond to different situations. Things you might have previously thought were harmless (e.g. flirting), you now have a big problem with. Things you might have previously thought were overkill or intrusive (e.g. electronic transparency) you now believe are reasonable measures.
So yeah. There is a lot of suffering to work through and mental restructuring necessary after betrayal. But since moral injury works twice, I'll still have to search for a better term for the loss of something integrity adjacent.