They have been laying off under performing TEAMS. These teams may have some really good people mixed in with the bad, but the good people already had other jobs lined up in other places around the company.
This sounds like typical corporate group-think to me. There are lots of reasons for underperformance. Many of the "bad" people might be great in another group, another company, or doing their own startup.
Granted, but my point was that you would think they are better at picking under performing teams than under performing individuals. It is much easier to see weakness in aggregate.