I mean, the law part is still completely obvious. If you have a part that scales proportionally with workers (p) and a part that does not scale with workers (1

I mean, the law part is still completely obvious. If you have a part that scales proportionally with workers (p) and a part that does not scale with workers (1 - p), then only the part that scales proportionally with workers scales with the number of workers (p / s), it is pretty much a tautology. The only reason why it is non-obvious how to take advantage of it in practice is that problems in the real world very rarely break down so cleanly into a completely serial piece and a trivially, arbitrarily parallelizable piece and even if you are lucky enough to find such a problem at a certain scale, the very act of breaking down the problem almost always eventually results in other previously ignorable constant or scaling factors becoming important either as you chop the problem into smaller pieces or as you scale to bigger problems. The difficulty lies entirely in posing the problem to be "solved", not the application of the law itself.