[anonuser123456]

Employment is a game of matching; the employer wants to match a skill set to a particular job.

It’s entirely likely people on these products don’t easily match internally.

The job market for people capable of working on Apple high end R&D is also likely much better at matching then Apples internal HR, simply because the market has so many more openings.

[neom]

Especially at Apple. Although I've never worked for Apple, I did spend a year at a company that built internal software for Apple, my experience was that their teams are tightly coupled and very, very long-lived (hence they had external software shops building internal tooling for them).