The worst will know they will have trouble getting a job elsewhere. The best might assume they are known to be the best, so they are safe. I would think it would be the middle people who would jump ship.

Nah, layoffs are too random. Being the best on your team doesn’t matter if the division is cut, or if the VP is making the call, or if your manager is disfavored, etc.

Most of the (risk averse) great folks I know have purposely found safe harbor over the past ~2 years.

Doesn’t mean it isn’t intentional. Lots of companies don’t really seem to have a concept of “best people.”

Also cost savings to consider such as severance.

Exactly. Companies really don't care as much about talent and performance as people think they do. Most of the time good enough is good enough. And companies almost always prefer attrition to layoffs or firings. Corporations are very conflict averse by nature.

This assumes that there's a significant difference between top performers and the next tier down, and that it's important to keep 'the best people'. In most businesses there are plenty of other good people who can step up if the best ones leave. Its also rare that someone is 'the best' at everything; people have a range of skills and you'll only be losing the person who's best at one or two of them.

Most people who think companies have a 'best person' aspire to be seen as that person, and haven't really thought about what it would actually mean.