well, this is let's run, so a 1 mile/day plan is really 5 miles/day including warmup and warmdown. wait, don't forget those secret uncounted 7 mile morning runs. 1/day = 85 miles/week at least...
one of the interesting things about this idea of using daily time trials to build fitness is that it has some merit. a mile run is a fine VO2peak workout and it would be interesting to look at data testing the approach -- even if it is only short-term. and for runners in the 1950's this is not all that much different from how runners (especially 800 and 1500m) were apt to train. if the training were structured this way, what pace might be sustainable or optimal?
1 x mile at 5000m effort might bring better results than all out miles. and you could improve the effect of the pattern by licking 400m hard, or running 200m hard/ 200m float etc... basically moving towards interval training or adding variation to cover all the bases.
every workout is a bit of a test, a trial. it might be hard or light effort or whatever effort but all the pieces fit together. a useful training schedule is in many respects, a single test workout also, the parts summing to a whole.