I have been trying to make a mental picture about the Delta-X Criterion. Where I agree is that when pushing to expand contrast keeping the speed near the normal EI one moves up on the curve which results in a steeper gradient (one could shorten the development as a result) and one gets away from the toe.
What bothers me is when pulling. Looking at curves left of the 0.1 speed point the curve has largely the same shape as right of the speed point. So shortining the exposure would work out mathematically.
But in my point of view in the shadows we have dark places next to light places, in the dark places we have even more dark places which I feel may have too thin a density.