> Maybe because when downsizing you pick the lowest performers that for whatever reason you haven't already fired

"Lowest performers" doesn't imply bad performers (e.g. a strong team of A & B players).

Also downsizing can happen in different ways. For instance: "we're closing this whole site and laying off everyone who works there," or "this project failed [due to bad leadership], so we're laying off the whole team."

There was an interesting comment on HN a while ago to the effect that "I have personally seen one team laid off and another kept, while everyone agreed that the laid-off team was performing better, because the rent on the building they were in was more expensive".