However, a new speculative thought occurs. If the autothrottle was engaged and one engine gently rolled back to, or near to flight idle with the autothrottle active and the other engine maintained climb thrust...the performance...specifically the rate of climb and/or the speed would be reduced from normal. The secondary flight control effects of the thrust asymmetry would be masked by the autopilot
I seriously doubt that is even possible on the 737. Which has only one servo channel to drive both thrust levers. The 737 therefore has “SPD” annunciated in the fma.unlike the 777 for example, which has 2. (Resulting in “L spd” or “R spd”)