You’re paying attention!
This is a good point to bring up and does warrant some discussion. I am traveling at the moment and don’t have a copy of the book with me so I can’t speak to your specific page references.
But, I think I can shed some light on your question that will still give you a decent handle on this whole polarized training concept.
In Seiler’s several studies he uses the percentage of workouts not time in zone. That way he comes up with the roughly 80/20 split. Studies looking at polarization using time in zones come up with averages closer to 90/10.
I think the important take away here is that the ratio of low to high intensity training is massively biased toward training in Z1-2. These meta data studies give averages so there is going to be some significant variation between athletes.
What Seiler and others have now elucidated is that the all to common opposite intensity distribution where 80% of the training volume/sessions is done in Z3. The current fitness fad of replacing the high volume of low to moderate intensity with frequent doses of high intensity training may be an acceptable model for fitness enthusiasts and non endurance athletes but it is not going to give the best results for those with serious endurance aspirations.
So, my recommendation is to use these numbers as guidelines rather than a strict prescription.
Be especially cautious of trying to emulate Kilian’s training. He is a unique individual. An outlier both in terms of his genetics and his training history. He and I spoke at length while working on the book. He was concerned about people trying to copy what he does. His polarization distribution is skewed toward the high intensity end because he races so much all year long. Not many folks can do that much racing.
I hope this helps,