I know many companies that do select whole teams, but it's also cleaning house time and the lowest performer from a previously non-impacted team will be included as laying off is easier than firing depending on where in the world you are.
Regardless, in absence of information, you cannot conclude that someone who was laid off was an underperformer. It can just as well be a member of a team who was considered lower-priority and disbanded.
He's describing a general bias that absolutely exists, whether it's always accurate is unrelated.