I think you've got a slam dunk if you can show some evidence that say... during a repeated, sub max single leg knee extension (with similar forces and contraction frequencies that the quad group would see during cycling or running at VO2max) that O2 extraction is incomplete.

If during whole body exercise that extraction is complete, and if the muscle group is worked in isolation with similar forces and frequencies of contraction and the extraction is not complete; it seems to me your argument would be proven and even Frank would come around.