It's a good observation that the Africans tend to do a higher proportion of fast running compared to Caucasians. But you have to remember that they are training at altitude, so these 'hard' runs they do might be hard efforts but the pace is relatively easy on the legs (for them; obviously 5:40 pace in a forest with rocky trails and steep hills for 3 hours is no joke, but it's not the same as pounding the roads at marathon pace). So it's possible for them to run hard more often with less recovery time. Besides the altitude, the hills have the same effect; allows them to work hard without moving the legs too quickly.
If you are training at sea level, it's probably best to not follow a schedule like Geb's but rather a model like the Hansons': every hard day is followed by no fewer than 2 easy days. And the easy days are reasonably controlled: 6:30-7:00 pace even for 2:15 marathoners.
Also, honestly, if your goal is 2:15 or slower, the Hansons are a better model for you anyway. Their methods have a high success rate in terms of getting people to 2:20 and from there to 2:15.
In terms of getting people from 2:15 to 2:10, the Hansons have shown they can do that too. Though I would agree that they need to get a few more people besides Sell to do that, before we describe their methods for that process as tried and tested. From that standpoint, the African fast-all-the-time approach might be a reasonable thing for 2:15 guys to try out. But the rest of us have no reason to think that a scaled down version of sub-2:05 training will get us to 2:15, 2:25, 2:35, etc.