That is different than for layoffs, which generally is less about rooting out toxic people and more about lowering costs. And people know it usually.
That said, anyone causing trouble for management or viewed as not pulling their weight will be the first on the list since management won't have to justify firing them.
Those are really stupid managers.
If you don't have docs it's a tough competition between having your more knowledgeable devs re-explaining what they know X times to X new hires, or letting new devs figure it out on their own which is both costly in terms of their time and more importantly, risky as hell.
Bad managers love risk though. Since it usually is a choice between speed now and risk later, it only blows up in your face later, and quite spectacularly, and everyone looks like heroes while they are putting fires out on overtime.
That said good managers probably don't tolerate that shit from bad managers under them and can sniff out a firefighter culture pretty quick.
I guess what I meant to say was, managers that value doc do exist. If they really do, they'll let you know.