I don’t see any logic in the Boeing advice in an idealised operation; what safety advantage does autobrake have over manual braking?
Researching this I find that Boeing’s recommendation to use autobrake on ‘slippery’ runways “
assures prompt application of brakes after touchdown”, but then cautions that “
autobrake performance capability is limited by runway friction” and that the published performance is based on the assumed runway friction (‘Stopping on Slippery Runways’ July 2001 et al).
This implies that the advice is to accommodate less than optimum pilot performance, yet recognises weakness in assessing the runway condition and selecting an appropriate autobrake setting.
However, a later version of the Boeing presentation
Landing on Slippery Runways provides a balanced view – use autobrake or manual (slide 35), use auto brake on wet / slippery runways (slide 36), but for manual braking on short slippery runway use full brake pedal pressure (slide 37). This also points out the hazards of incorrect (too low) autobrake level for the conditions and that autobrake used with reverse may not be as good as manual braking with reverse in low friction braking conditons.
As I recall, the need for autobrake was driven by poor manual braking performance during RTO’s. Subsequently the system has been ‘sold’ to operators as having economic advantage and for passenger comfort, neither of which should dominate operations, particularly in the conditions cited by Boeing.
IMHO, autobrake has contributed to many incidents and perhaps some accidents due to habitual use without appropriate thought or background knowledge; hallmarks of automatic dependency.