HRE, I agree with you that the tables are both one of the greatest values of Daniels' books and also the biggest weakness. They are the biggest weakness because, when used properly, they can be so useful that people assume that they should always be followed. Those people are wrong.
I don't think that someone who has read Daniels would feel compelled to hold 65s for their 400s in the circumstances you are discussing. In fact, if they read the text, they would understand what the purpose of a 12 x 400 workout is in the overall training plan.
In this case, the purpose of 12 x 400 in a Daniels world is to improve running economy. Daniels spends a fair amount of time in the text of his book discussing how if your form is breaking down in a running economy workout because you are going harder than you can sustain, then not only are you not accomplishing the goal of the workout, you are undermining the workout. Just doing a quick glance, I found (all in Chapter 9 of the 2nd Edition of DRF):
- this point by him on what "R" pace is: "[A] variety of training paces can be set aside for repetition work."
- this point by him regarding recovery periods for such a workout: "If the recovery is not adequate, stress mounts, mechanics deteriorate and the purpose of the training is destroyed."
- this point by him "If you reach a point at which resting four times longer than your're running is not enough rest, either you've had enough for that particular session or the pace has been too fast and you should slow it down for the next run."
These are not the words of a guy who is trying to lock someone into specific cookie-cutter paces. This are the words of a guy who is trying to impart general principles to be used in training, and then includes data that can be used as a starting point in finding out how to apply those principles to your particular circumstances.