I've always had a little bit of a gripe with how the "communications complexity" is presented here. As if the only way to communicate on a team is to have everyone stand in a circle and yell at everyone else.
In reality, there is very often opportunity to take 1 project with ~3 engineers, and break it into 2 smaller projects each with ~3 engineers and run them mostly in parallel. Do your best to isolate those projects, but have a point of contact (EM, PM, tech lead) between the two teams to coordinate whatever dependencies are unavoidable, etc.
You'll notice, that this is just a smaller microcosm of how every company is actually structured anyway. There's still diminishing returns, but most people on the team never need to communicate directly with people outside of their project.
Is this not just a different manifestation of the third key observation?
"Division of Labor: There’s a limit to how effectively a task can be partitioned among multiple workers. Some tasks simply cannot be divided because of their sequential nature, and for those that can be divided, the division itself can introduce extra work, such as integration and testing of the different parts."
Pretty sure it simply represents the upper bound of communication complexity. Any management of it can improve coordination. The conceptual lower bound is that each additional programmer adds 100% more programming speed.
In reality, there is very often opportunity to take 1 project with ~3 engineers, and break it into 2 smaller projects each with ~3 engineers and run them mostly in parallel. Do your best to isolate those projects, but have a point of contact (EM, PM, tech lead) between the two teams to coordinate whatever dependencies are unavoidable, etc.
You'll notice, that this is just a smaller microcosm of how every company is actually structured anyway. There's still diminishing returns, but most people on the team never need to communicate directly with people outside of their project.