I like the theory - if you don't do so many 'huge' runs you don't leave yourself so weakened and at risk of catching colds either.
I haven't folowing a hanson plan but m still unconvinced that it really trains you as well the more tried and tested approach.
I do think that '20-21 miles' is a distance that comes from back in the day when marathons weren't as mass appeal as no. So that represented a 2:00-2:30 steady paced effort to most plan followers - as a result may be 22 miles is a bit long for a 'get me round' 4:30 target person.
Fergster- Ive heard that the body reacts and supercompensates to a major training race/stimulus over 10-12 days. So this is a good time to have your last big effort during a marathon taper.
Hwoever ive also read that the marathon isn't just a big stimulus and takes a lot more out of you. Maybe some bounce back improved just in time for an even bigger effort two weeks later but I cant imagine that applying to everyone