It's very common in these situations to target every org in the company with a goal of X% reduction. If a small fraction of these teams now need extra headcount, easy enough to allow those teams to hire. Usually you don't keep the severance if you return in under X days.
I've personally been laid off, only for the post-re-org team to hire several people, including asking to rehire me. It's rare, and those affected should probably plan to find new jobs, but it happens.
I've never worked at a rational company. I'm not sure that's a thing.