That's true, but I think on one hand these are fairly rare cases compared to the whole industry while on the other there is also the point that these divisions might not be as stable and long-lasting as one might expect.
To the first point, they're rare but industry is massive so their total absolute size isn't that small. And if you're a tenured professor in a semi-related area then it's not hard to land in one of them.
To the second point, it's true that the research focuses shift over time but if your research area fizzles out you can either shift to a more applied position or move back to academia.
To the second point, it's true that the research focuses shift over time but if your research area fizzles out you can either shift to a more applied position or move back to academia.