1. Consistency is the most important thing.
2. When we do our Magic Mile as part of the training program, we run/walk our warmup mile, then run the next mile as the MM.
3. Once we have our target pace, we do the training runs at the "recommended" run/walk intervals for that pace, but at 2 mpm slower, and even slower on really hot days and days when the runs are going to be really, really, long. (In reality, each pace group sets its own tempo based on the level of its members.) It's assumed that in a race situation that a) the speed work that you do during the week separate from your long run and b) adrenaline, will give you the additional time to meet your target pace.
4. After having said that consistency is the most important thing, it's also important to be flexible. Even if you've trained at 3/1, if you get into a race situation and find that you're struggling, switch to 2/1, or even 1/1, whatever gets you to the finish line.
Or, as VerticalChaos is doing, modify the run/walk to fit what works for you. It's all about getting to the finish line feeling good, and recovering after! Trying to comprehend Jeff's books can be too much for anyone - even after 4 years in the program, I pick my pace group by the interval I want to run, not by my MM. I run 3-4 days a week, not following anyone's plan, but doing a mixture of speedwork and some hill workouts.
Jackie