The agencies I've worked with are pretty good about this. They rotate forensics specialists in and out of particularly traumatic work like child protection, they have support systems in place, and they give their staff plenty of downtime. One place I'm familiar with has about 30% of their team out at any given moment.
The same can't be said for other people down the chain, such as detectives and prosecutors. They absolutely are told to just suck it up.
While I was never exposed to csam or explicit violence during my time working DFIR, I saw plenty of cases where good, honest, hard working people lost their entire life savings to scammers. Some lost over $1M and never saw it again. Ten years later, I still remember the sense of shame, hopelessness and loss these people suffered. I wouldn't say I was traumatized by it, but that sort of thing definitely stays with you.
I gave up digital forensics because of this.
This is recognizable as variant of the non-constructive "I told you so".