Yes, the original topic was about whether the OP might be able to run 2:19 on 70-80 miles a week and my initial response was that it could be done and had been done but there was only one way to find out if he could do it. The topic has eveoved since then. My response that you're responding to was to someone talking about Letsrun posters being stuck in a mindset that more mileage is better and I pointed out that there is very good historical evidence for maintaining that belief.
If we knew exactly what genes someone inherits to make them good at distance running we could talk more accurately about their distribution but we don't know that. But the larger numbers of people running lower mileages should see that group represented more strongly at the front of major races. When you look at at least sixty years of better results from high mileage runners it is logical to think that the high mileage plays a major part in those successes and to keep thinking that until there is a good body of evidence to the contrary.
You other points represent ideas that have come into the sport today and are largely accepted but were once different. "Available time" is subjective but running 100 miles in a week does not, to me, seem to need that much of it. In the days when we mostly all had to work full time many of us ran that much or more. A 45 minute lunch run and an hour after work didn't seem like a lot of time commitment and we didn't have pro runners making our own situations seem difficult. Yes, wanting to reach your full potential was really important. Still is. Maybe it's the most important thing. Is there a gene for that? And yes, it's hard. That for me was the appeal. If it were easy everyone would do it.
All of that said, there are plenty of people who get really good results on fewer miles. I have nothing but respect for someone who wants to run as well as possible within the limits of his/her life. I wish Below Average the best and I think what Coach JS offers is very useful for someone like that.