PF retards the thrust lever because he is hand flying and can coordinate thrust reduction and rudder input.
Mana, as I said, don't rush it and it is no problem for the PF to FLY, while the PNF/PM closes the throttle. Done it many times in the sim over decades. When I'm ready, I'll look to check that the PM has got his finger on the correct throttle, then call "confirmed". Then I'll continue flying.
The biggest problem with Boeing SOP is the lack of challenge and response in normal operations. If the captain is FP, the copilot will do the cockpit preparations, read and respond the preflight checklist, and also read and respond the after takeoff checklist. The captain can read the newspaper most of this time. He is supposed to check what the copilot is doing but there is no active involvement.
If a company doesn't assign duties and responses for each normal checklist item, it shouldn't be in business. If there is "no active involvement", is that a failure of the procedure/SOP?
As for the captain or the FO making the fuel switch selection depending on which area of responsibility it is in, when airborne with a failure or fire (or any other non-normal, for that matter), it just goes to show how silly an idea it is. There should be no "area of responsibility". Each normal action/check should be allocated to a specific crewmember, and the checklist should be written that way. During Abnormal and Emergency drills, to have the PF leaning up flicking off/cycling switches because they are on his side of the panel on a particular procedure just doesn't make sense to me. Certainly, the switches on the centre console are in easy reach of both pilots and the "area of responsibility" system is ludicrous. Maybe that is why Boeing conveniently ignores it when it suggest the PF closes the throttle during a fire...
