Are these good ideas (Fred Brooks “The mytical man-month” 1975) ? Does anyone use them ? Did Collins ?

-The Mythical Man-Month
Assigning more programmers to a project running behind schedule will make it even later, due to the time required for the new programmers to learn about the project, as well as the increased communication overhead. When N people have to communicate among themselves (without a hierarchy), as N increases, their output M decreases [...]