Hudson.
A level, idle thrust deceleration may be the most efficient in smooth air but may be a poor choice when descending into turbulence. A decelerating descending speed bleed flight path (as mentioned by LEM) can often be far more efficient at satisfying passenger and cabin crew comfort considerations as well as permitting a bit more flexibility at achieving your desired energy gate.
I just reread my FTCM which covers all models and I would have to read a hell of a lot into it to come to your conclusion. Unless you have a communication from the author that states that his/her intention was that anything other than a level deceleration was not permitted (interesting for stabilised approaches!), then I think you are inventing a bit of folklore.
I think level decels are the product of laziness and a lack of finesse, but remain as part of every pilot's toolkit. I am just off to search out some words that I can claim to support my case.....
Stay Alive,