Why would it "clearly" be better for pax going from Edinburgh to Tokyo to transit CDG than LHR? As the great circle route passes north of North Cape and over Russia, it would be more mileage, more fuel, more CO2, more £, and more noise!
Do you hold a brief for the French national budget? Or is it that you are a Scot Nat so extreme that you would rather see taxes go to France in their entirely, 100%, than see them go partly (less than 50%) to England and indeed Wales? Certainly there is no environmental or economic reason. Clear as mud.
Approximate EDI-CDG-NRT route
Approximate route EDI-LHR-NRT
As a comparison, approx direct route EDI-NRT