The Boeing Company is protecting itself from the law by stating this in the FCTM, as there have been longer flares due inadvertent trottle movement during landing.
The Airline is aware of the odd go-around going wrong without proper thrust setting, and implements the landing procedure with A/T armed.
My previous carrier publishes only dual autopilot approaches in VOL 1 to circumnavigate this responsibility.
Pilots are getting confused are they think they can fly planes safely while monkey flying SOP`s.
At the end of the day, flying remains still a profession.