rudderrudderrat, JT, could the issue be associated with “the most adverse configuration”, which may not be the same configuration (wt, cg) for each speed, and/or involve the same defining parameter for the limit of control, e.g Vmca can be defined by the aircraft experiencing stall before a control limit.
A further thought is that for Vmcg there is some lateral force from ground contact, and although this is removed at liftoff, the transition to controlled flight with application of bank (Vmca) is a dynamic maneuver, perhaps not necessarily constrained to the test conditions which establish the speed, i.e. test conditions may not translate directly to practical operating conditions.
If Vmcg and Vmca do not refer to identical conditions, any attempt to compare these speeds or the aircraft’s ability to fly at one or other speed in identical conditions would be impossible.