once the reputation of a team in Apple is established, the CVs of every team member becomes more desirable around town, even without their skills having changed 1%. same for Tesla, one their cars started shipping in quantity and people realised they won't fall to bits in two years time, anybody on those teams get a halo on their CV. price to move them goes up considerably in a skills shortage.Sorry, I have no definitive knowledge. However, none of the people at Apple that I know think that this has happened. None of them have definitive knowledge either, but they do know their teams. So... I'm skeptical there's a problem. I can't disprove it though.
Edit: Let me be clear, people leave all the time. Even some of the rock stars. But others join. That's normal. I'm talking about an unusual level of churn, as described in those news reports you mentioned.