That 16 workers running at 16x overseen by 4 line bosses and 1 CEO will suffer more coordination failure that can be avoided by running 256 workers at 1x with one CEO running at 21x, seems plausible and even likely if you assume these are human-like minds.

Robin's scenario is 256 workers and 64 line bosses running at 1x plus one CEO running at 21x who directly oversees the line bosses not the workers (you can check for yourself here). This offers no coordination advantages over having 16 workers, 4 line bosses and one CEO all running at 16x, as far as I can tell.

I'm not sure about that. What I've seen of the management literature suggests that the complexity of coordination and oversight problems is strongly nonlinear on the number of workers overseen, and clocking faster would produce only linear improvements. It might still make sense to run the CEO at a faster clockspeed, since that role has to deal with additional coordination problems that aren't entirely under the company's control, but this line of thought suggests to me that smaller numbers of more individually productive workers would be more efficient overall than maximizing the workforce size.