First of all, this is a very good point; but I would still like to track you down and feather you with HRE and Glenn, so please let us know where you live! ;o)
Now, all the seriousness, you've got to realize that the Old Man had a tendency to exaggerate a bit to get his point crossed. Following this "best aerobic" stuff, he said something about Snell running 150 miles a week with morning jog. You can ask Dr. Snell; that's a bunch of BS. Why did he do that? Simply because he got tired of people telling him that 100 miles a week is not enough. You may not believe this; but people actually ran more than 100 miles a week back in those non-professional days. His runners did run more than 100 miles a week at times; did morning supplementary jogging; but he was just making the point. Just as someone else said it; you can not, and should not, just read one line and jump to conclusion. Ron Clarke, for example, said in one of his interviews; that people say that he ran 150 miles a week, 3 times a day and so on. He said, he tried this 3-times-a-day stuff once and it was too much and dropped it quickly; but when he mentioned that once, the reporter quickly calculated and next thing he knew, that became his career-long routine and his weekly mileage calculated "the best mileage of 3-times-a-day" X 7 days. Just as Coe's 35-miles-a-week-year-around deal, that's a bunch of BS.
Second; his deal with "best aerobic effort" is, once again, his attempt to get his point crossed that it wasn't just "jogging". Americans came up with the idea of "Long Slow Distance" which was also associated with Lydiardism. Basically, what happened was Arthur only emphasized 100 miles a week. Some people tried it and they weren't as fit as Arthur's runners and the only way they could manage 100 was to go as slow as possible. To justify that, they came up with this "LSD" method. It's not Lydiard at all. But, again, people associated him with "LSD" and he got annoyed by it and, his typical fashion, told everybody "screw you" and said "we never ran slow; we were runnnig damn fast!" Now, here's the thing. When you look at the schedule, as someone else already pointed out, they are all at different effort level. You could probably safely assume this 3/4 effort or 1/2 effort is the marathon pace (or half marathon pace)...or LT pace or sub-maximal pace or whatever you want to call it. Greg McMillan and I were talking about this and, yeah, we feel there is a need to straighten out when so-and-so says this, this means at around this effort. It seems like everybody's using different names for the same effort level.
Thirdly, when Lydiard came up with his program, the marathon races, at least in NZ, were won in about 2:30. If you define "best aerobic pace" as marathon pace, it's not that fast. Snell ran his one and the only marathon in 2:40. That's 6-minute pace and he was easily circling around 22-mile Waiatarua counrse with a 3-mile long uphill at that pace during the build-up (well, maybe not that easily...). But then again, if the marathon guy like Magee, whose marathon time I think was somewhere around 2:16, going around Waitak at that pace, his "best aerobic effort", or sub-maximal effort, was applied in his 10-milers.
Lastly, I think Arthur was mainly referring to Derek Clayton of Australia. Actually I think he, and perhaps Jim Peters of England in the 1950s, were two runners I can think of who did lots of mileages at close to their marathon pace. Some people, as long as they keep aerobic, can to that and there's nothing wrong with it. There's nothing wrong with keeping it nice and easy; but at the same time, there's nothing wrong, if you CAN handle it, to keep pushing the pace.
It's funny, though, most people criticise Lydiard training for too much mileage and too slow. I haven't heard people complain his training "too hard". It's like; you can't win... We however do have a heffty goal of reproducing Lydiard's books with footnotes from various people. There are way too many "myths" surrounding "Lydiardism" and Arthur himself, undoubtedly, was responsible for some of them. We welcome questions like this. The more we think about it; the more we get the ideas of what we need to do to clarify those myths. So thanks; we'll reward you with tarr and feather! ;o)