The art of engineering team focus: less is more

> Take your top priority and put as many developers on it as you can—until they're literally stepping on each other's toes. Only then should you move on to the next priority.

sounds like what Fred Brooks warned about in The Mythical Man Month: Adding manpower to a late software project makes it later [1]. What am I missing?

[1] https://en.wikipedia.org/wiki/Brooks%27s_law#:~:text=Brooks%...