Over and over and over again it has been shown that there are many different ways to train to have success in distance running; higher mileage or lower mileage, very easy days or quicker recovery runs, lots of intervals or lots of tempo runs, many long runs or no long runs, etc. etc.
Despite there being so much evidence of different training methods leading to success, people tend to believe that their way of training is the best way. If someone found themselves improving from increasing their mileage quite a bit, they think it must be the right thing for everyone, even though there are many examples of it not working for someone else. Weldon had some success by slowing his easy day pace down, sometimes as slow as 8 minute pace. That is great because it worked for him. I have known many other world and national class runners that trained very differently and it has worked for them. For the level that Rupp and Farah are at, doing the majority of their running at sub 6 minute pace seems very logical, just like it does for Chris Solinsky. The problem is that since these are three of the better runners currently, it ruins the theory of so many that you have to run really easy on your easy days to be successful. No you don't, or at least many successful runners don't. Since it ruins their theory, many people just refuse to believe it is true.