Hawk,
my reasoning was that we have to chose a single speed and altitude. Given that we are probably above OEI ceiling but below AEO ceiling we are already too low for optimum 2 eng endurance so we either climb now or start throttling back both. If we chose the single eng ALT and speed we get the bonus of height in hand. That gets us ahead of the game as we drift down with one at MCT. Then we only misuse on engine as we throttle back.