I mean some people that work at abattoirs have PTSD, it's not unique to seeing humans slaughtered.
I think both things are true. The same way someone who works in the business of slaughtering barn animals won't go vegan or even vegetarian, even if they have PTSD.
It's got almost nothing to do with "seeing too much slaughter" in the case of the iof. It's actually laughable (and sad) that some people on this site really think those people are somehow getting tired and traumatized by the genocide.
The iof literally say why they're feeling this way, it's quoted in the article
"They return to the same buildings that they cleaned, each time trapping them anew. They have been to Al-Zaytoun neighborhood three times already. They understand that it is futile and pointless.”
They feel that they're doing meaningless busy work that's also getting them killed. Mind you, if they thought their slaughter was actually doing something they'll happily keep it up so long as they're not getting fucking washed by resistance fighters.