I've finally found the time to read through the whole book (great read btw, I enjoyed it and am looking forward to try to improve my own FM-skills)
I came here to bring up this issue as I was confused because of the mention of "Low defensive line" while the screenshot of the tactic mentioned "Much higher defensive line", and I couldn't remember any part where this was explained.
If I understand it correctly you played with a much higher defensive line for a while, but after a while changed to a low defensive line? Did you change the Line of engagement as well or did that one stay on much higher? Really curious about this as I think I noticed a lot of FM-players change the line of engagement as well when they lower/higher their defensive line.
Thanks for your time!