Just a guess but I pressume the A/T arm in the preflight is to bring the procedures in line with other types in the boeing family.
Well if that is true I am amazed that Boeing has made this change. Do we have to go down the route of "commonality" so far that we jeopardise flight safety? I see this as a type of "dumbing down". If I am flying a B777 then I follow the B777 checklist/procedures, if I fly a B737 then I follow the B737 checklist/procedures etc!