The problem is that a true company-wide firing of bottom 2% of performers is impossible - you would have to somehow compare and rank people with vastly different roles to pull it off. So the way to do it is to first choose unlucky departments and set a quota for each department, then choose unlucky managers and let those managers choose unlucky employees. Which makes it a lot more similar to a layoff than the company likes to admit. These employees may be perfectly solid workers but now they have to bear a stigma of being fired for "performance" reasons.

I had a manager friend whose company went through a "not-layoff" when approx. 2% of the workforce were let go. His group was among the unfortunate ones so he was told to choose one victim among his subordinates - but there was no one with unsatisfactory performance in his opinion. Still he had to choose. Didn't improve his morale that much - he quit shortly afterwards.