Earlier quoted context omitted.
Of course just like everyone on HN am aware of the book and heard this quote a billion+ times. And of course I know it's badly misused in this particular case (as it often is).
software development parallelization works about as well as it does for actual software, ie non-linearly at best. Add to that overhead/mistakes/difficulties caused by "synchronization" and you come to the conclusion that a significant amount of that "30 man years" of software had to be just discarded when rebuilt
EDIT guess this is just rephrasing of your point, in a way.