I understand it may seem speculative. However, it's understood that East Africans can sustain/function at a higher level of lactate at threshold, but can not produce the same peak levels. For instance, many East Africans can sustain closer to 6 mmol of lactate at threshold vs. closer to 4 mmol for most well-trained Euros.
The greater the aerobic development, the more lactate that can be cleared and the greater the range of the athlete.
Alan Webb, whose accomplishments and range are truly incredible, very likely would have been better served to develop his aerobic capacity more so he could clear lactate better. Instead, he seemed to focus on the ability to create and utilize as much lactate as possible. This sort of pigeonholed him into being an 800-1500 guy, although he didn't take the 800 as serious as I wish he would have. I think he could have run some very special 800s, but that's a different thread.
It is not unprecedented that someone is world class at races lasting around 4:00 on up to 60:00+. Witness Chris Boardman, who at one time was the very best at the Individual Pursuit (lasting about 4:10) and the hour record simultaneously.
The marathon is reaching a level of professionalism that requires the best in the world to be world-class or very nearly so at every distance from 1500m up. Even in the 800m, if you can't train into sub 1:50 shape within a month or two of specificity for it, you will not be able to run with the greatest marathoners in the world.
This is a real golden age of the Marathon, where one must be a renaissance runner of sorts, being very well developed at all distances.
The one who can hold the WR and win the major championships in the Marathon shall have the honor bestowed upon him as the greatest distance runner in the world.
I reckon Bekele will be able to pull this off in the next year if Mo doesn't do it before him.