The mythical man month is about communication between people and the amount of work to be productive in a project. It's about people colliding with programming.
It has nothing to do with a vague statement that "eventually" you have diminishing returns on processors (of course there is some limit even though different tasks could be many orders of magnitude apart).
For Brooks the communication between people starts to dominate the time spent the more people you add, so it will eventually become the bottleneck.
For me it's an interesting parallel. Feel free to come up with your own conclusions.
It's completely obvious and the "eventually" is where anything interesting happens. This comes from the early days of computers which is why something trivial became a supposed insight.
For Brooks the communication between people starts to dominate the time spent the more people you add, so it will eventually become the bottleneck.
Not just the communication between people while working in general but the communication to get someone involved in the project weighing down the people who would be making progress.
Feel free to come up with your own conclusions.
I did come up with own conclusion, the only similarity is the word bottleneck.
One is basically 1 + 1 = 2 and the other is a warning of a non obvious situation that comes from lots of experience and effort.
One is is good information from lots of experience, one is "the parts that don't use more cpus don't speed up with more cpus".
Unhelpful nonsense about running software vs battle won experience about making software.