[banannaise]

There's this ridiculous idea that management is partially responsible for the productivity of every developer, which means their salary should be increased commensurately.

You could just as easily argue the reverse: every developer is partially responsible for the productivity of management (whose productivity is zero if the devs get nothing done), so the devs' salary should be increased commensurately.

A hierarchy based on promotion and with increasing salaries isn't based in ironclad logic.

(In fact, you can see this in (in my opinion) two of the most important roles on a development team: the agile lead and product manager! Neither of them are hierarchal managers, yet both influence the direction of the team in critical ways. It works really well; far better than if either or both of those roles is filled by a hierarchal manager.)