Handling the Big Jets is indeed a fine book and a must read for any pilot transitioning to jet aircraft. But the advice from D Davies, though fundamentally sound, harks back to a very different time. Automation (including flight directors) has come a long way since the book was written. A modern AFDS system when used correctly is invaluable. I think the updated version of the book, were it to be written, might include a section on the importance of appropriate use of automation and understanding FMAs and what different modes actually do for you. Frankly, the latest generation of jet transports are not designed to be flown manually "with everything turned off". That may leave some pilots aghast but it's true. Hence practising manual flying skills is a regular item in recurrent sim checks - arse about face for many of us, but that is the way the job is heading.
This particular incident has so much more to it than just blindly following the flight director.