By transferable, I mean skills that are useful outside of our big tech bubble. You might not want to go out as money is very nice, but still good to know you can do something beside computer beep bop.
I think staff engineers are slightly more common than first level EMs, but senior EMs are slightly more common than senior staff. Beyond that, it's small numbers and hard to draw conclusions. The nuance I've felt is that promotions to staff and up on the IC ladder are more in your control, while EM promotions are very much about being in the right place at the right time, in addition to being ready for the role.
I have worked at "normal" companies as well, and I think the EM role there is slightly different? To me it seemed like it's people management + technical, while in the tech bubble, that would be called "TLM". "Pure" EMs are mostly doing people management only, with strategy and XFN alignment. Does that sound correct to you?
I come from Russia, we're not exactly known for great people management, and I'd say management up to department head is expected to handle the tech part as well even in larger companies such as Yandex / VK. This fits your definition of normal companies perfectly.
That’s going to depend a lot on company (and how they define staff vs senior; that varies quite a bit).
Of course, companies on that scale don’t really have senior EMs in the Big Tech sense, either.