One word for 'pyramid' communication

Solution 1:

There isn't a single term, though "silo-like," or any other conjugation of "silo," might fit. What you're describing is an information silo, exhaustively explored by Gillian Tett in "The Silo Effect."

An information silo ... is an insular management system in which one information system or subsystem is incapable of reciprocal operation with others that are, or should be, related.

In this case, AA and BB cannot directly communicate, but must go through their bosses, who should have better things to do that facilitate communication between their employees (if they don't, they don't need to be there at all). Any communication must travel to the top of one silo, transfer to another, then come back down, with a loss of efficiency and probably context. Information silos are considered in the West to be a very Bad Thing.