Not theoretical...real world. No speed brake, power off descent compensating for wind, weight and airport arrival pattern, adding power at ~1,000' AGL, if left alone by ATC, which obviously wasn't always the case. .......... snip .........
To be clear, at same Mach/airspeed descent schedule: heavier weight...longer glide. Lighter weight...shorter glide.
OK, that makes sense. I took the post to mean a minimum fuel decent which involves operating at best L/D. That's why it didn't make sense. Now I see the examples were idle decents using the same speeds at widely varying weights; quite different from a minimum fuel decent.
For reasons discussed earlier, such things are never done in the airline business except (perhaps during a fuel emergency) since airliners usually have sufficient fuel and not much extra time or money. However, back when I was one third my age and one half my weight I flew fighters for the U.S. Navy where we used a best L//D decent frequently. We had plenty of time and money but we were always out of fuel.
