You are right that this is something to consider. In my case the "realm" think was emergent and not enforced at all, but it was a bit implicit that if possible,

You are right that this is something to consider. In my case the "realm" think was emergent and not enforced at all, but it was a bit implicit that if possible, you ask Bill his advice before rewriting a function of his model. The lead dev was still nosing around everywhere and had authority to call a piece of code defective and impose a rewrite. One of the important function of the project manager is also to communicate clearly with upper management about what the team is and can do. We were working on a product that was not deployed yet and our priority was to release a functioning version ASAP, so redundancy was irrelevant. We had n features to develop, assigned to various developer. When one developer is on holiday, their features did not advance. We worked around it thanks to our modular architecture. It meant that sometimes, <urgent but usually irrelevant feature> was impossible to code before <meeting with potential client next week>. I scheduled or denied those. This team and project structure is optimized for fast development with an heterogeneous team, not for reactivity.