As far as I can see, the only situation where an on the step level off would provide benefit is where there's a drag rise & then drop with incr. speed eg transonic to supersonic.
If the a/c has insufficient thrust to overcome the maximum drag, but sufficient to once the drag has reduced a bit then trading altitude for speed + max thrust could allow a final speed to be greater than without using a step. Effectively the additional height was used to store & then rapidly release a bit more energy to overcome the drag 'bump'.
Otherwise I can't see it. If you have thrust to climb then you have thrust to accelerate and eventually the steady state speed will occur when T=D.