The line manager and lead developers are not unlike non-commissioned officers. They are supposed to be able to talk to the grunts, and even though they don't do the "shit", getting shit done is not abstract for them. They know how to do it in a more concrete way. If they didn't, nobody below them would respect them. (Though I have heard tales of new NCOs being sweated by their reports because they clearly did not know anything in a concrete way. They were either going to learn or they were going to be forced out.)

For everyone else there's a lot of up-or-out. If you've been a middle manager for 20 years there must be something wrong with you.

In my experience, the Army was the same. If you saw a 18 year E-6 he/she probably had a problem staying out of trouble or were just incompetent.

Edit(context): Active duty in a combat MOS.

Its not obvious but the laundry files occasionally has a few mentions that might pass unnoticed by a non brit.

I have worked at an ex civil service place and there was a direct mapping between grade and the equivalent rank in the forces.