Organizations are structured as trees as a strategy to combat N^2 complexity. You talk up, or down. The tradeoff is of course N^2 relationships still exist in reality , so you duplicate effort, and sometimes collide, but it's a good tradeoff.
I think it’s more like an adhoc graph that’s more dependent on the task than the organization. Tree based management is only useful for reporting and dictates. The actual work is more like “I need to get X done, I need to work with I,j,k to do it.” Often the real issue is NOT that it’s N^2 interactions, but the space for identifying who I,j,k actually are is quadratic and there’s no index. This is often the immense value of “lore masters” in a team - they have an unnatural ability to know who to talk to about what. If you don’t have one in your team, get one.