Training Question

As far as fall back weeks neither of the plans (an old EN plan and Matt Fitzgeralds book) have them besides their test week or taper weeks.

Fitzgerald's plans most definitely have what I would consider "fall back" weeks. They are labeled "recovery" in his book. From his book:

Step Cycles
Step cycles are four-week blocks of training in which the second week is more challenging than the first, the third week is more challenging than the second, and the fourth week is a recovery week., in which training volume is reduced 10 to 20 percent. Training in step cycles is much better than training with less week-to-week variation in training volume. The incremental training increases in the first three weeks to ensure that your fitness moves in a positive direction with minimal risk to injury or exhaustion. The recovery weeks taken every fourth week allow your body to fully absorb recent training and prepare for still more challenging training in the weeks to come.