Unfortunately, “getting on the step,” seems to have two distinct aspects. The first is a process or flight path maneuver to get to the best-range cruise condition. If the plane has only modest extra power for acceleration, it avoids the long time-constant of level-flight acceleration to best cruise speed. The second aspect is the idea that the cruise state reached by this maneuver, the final “step” airspeed, is extra fast; a hysteresis situation that requires a certain approach path. Many (most?) pilots don’t believe that the final speed is anything unusual.
The 1945 Boeing POH recommends climbing 500 ft. above the intended cruise altitude for each 10,000 ft. of cruise altitude. They call the best-range speed ‘the step.” It must have been the common term at that time. They never claim that it is extra fast.
In Sweeney’s description he is repeating the maneuver process again and again. So the question is not; is the final speed is extra fast? But, is the average speed of the maneuver faster? Is it faster than what? I think that it should be compared to a flight path with a constant descent rate at the best-range speed. The descent rate allows the power and fuel flow to be reduced. As Earl1947 points out, as the weight decreases you must re-trim if you keep the same power, and the speed will increase. Is this what Sweeney was doing, or was the descent and flare more emphatic?
Climb to your cruise altitude. Start a watch. Wait ten minutes. Note your speed.
Climb above your cruise altitude. Descend to that altitude. Start a watch. Wait ten minutes. Note your speed.
They will be equal. You can accelerate up to it or decelerate back to it.
The simple fact is the extra time spent climbing through your cruise alt and mushing along at a higher altitude with even less excess power will more than offset any time saved a accelerating in a descent to the cruise altitude.
There is no step.
The step is a mythological technique that gives one extra knots for the same power setting in cruise. It is an impossibility.
B-29 instructors have said it made no difference despite it being "official" technique. They taught it that way only because they were under orders to. It made no difference.
As for trimming, that's a given. What's so magical about that? Nothing. If you move the CG aft you decrease downforce from/bythe tail. That will gain some performance at the expense of stability. If there were such a thing as a step due to aft CG the decreased stability would offset the supposed gain. In any case, one bump and you have to repeat the whole process.
I burn my tanks from the front to push the CG aft. It helps a tiny bit and when I am over the Atlantic I want to save every pound and gain every advantage. But this is not the fictitious step.
Columbo and Garrison made the point that the area of reverse command and cruise can be close together. There are two speeds for every power setting, but usually they are dozens and dozens of knots apart. Even in a Cessna 152 they start 70+ knots apart. Modern jets can have a spread of 100+ knots at 41,000 feet depending on wing design and weight. If they're only ten knots apart in a B-29 or a B-24 one could get the false impression of a magical step.
Regarding descents... There is an optimal place to begin a descent. Wait too long you waste gas for staying in cruise thrust when you could have reduced. Descend too early you waste gas for various reasons including increased burn and loss of True Airspeed. For every 1000' of altitude you descend you lose two percent of your True Airspeed. If a descent is flown incorrectly your fuel mileage and range suffer.
Would a B-29 be slick enough to gain some advantage by accelerating in a descent then leveling off...decelerating...then repeating the process? Would a constant rate descent have the same result? I know what my gut tells me.
