Hi CabinMaster,
Where do you stand with your first statement
Climb and Cruise speeds are the same, at least for a jet that cruises above cross-over altitude. The less well known "green dot speed" changes with weight.
Since "green dot speed" or "minimum clean speed" change with weight, and ECON climb varies as a function of (min clean speed), have you convinced yourself now that ECON Climb & Cruise speeds do change with weight?