I think that there is a poster here who can definitely show how EK can be where this regulation does not exist in actually giving nothing for an involuntary downgrade

If the regulation specifies that 75% is the entitlement, then it is perfectly reasonable to demand it. In fact on such an example of AMS-LON, there is no excuse whatsoever for a downgrade to occur due to the cabin size being flexible

If having to do an involuntary downgrade , then it would be silly of the airline to choose someone where the compensation would be so high

The regulation is not poorly worded in relation to downgrades at all imo; it seems particularly clear and unambiguous and the regulations are aimed at being a deterrent to the airline