Well, these days I may well be a typical 32:00 5k runner. But the point is I didn't want to be a 19:00/39:00 5-10km type so I ran a lot to be more than that. Yes, I enjoy running. No, I was not fast.
But you're changing the debate now. Your original question was whether running 100 mile weeks will make you faster. The answer is that it will for the most people. Whether someone running on the high side of 30 minutes for 5 km wants to or does run 100 mile weeks is irrelevant. IF most of them did they'd be much, much, faster.