Just to be clear, the second flight (AMS-ABZ) was actually cancelled, was it not? And getting on the original 11:40 MUC-AMS would not have gotten you to ABZ any earlier than the time at which you eventually arrived?

If so, I can see the logic of what they were doing: they put you on a later flight as there was no point in having you wait in AMS longer. Admittedly, they should have put you on the 2:15pm from MUC to connect to ABZ on the same day but that is what eventually happened anyway, so no harm done on that particular front.

As regards compensation, there is caselaw to the effect that compensation is not due when you are IDB'd on a flight and put on a later one if your arrival at destination is not delayed (IMO, this is a debatable of the Reg but, unless the ECJ overrules itself, it is the 'correct' one for the time being).

Your situation is slightly different but, going by the logic of that case, since you could not have arrived at ABZ any earlier even if they had put you on the 11:40 flight (given the cancellation of the original AMS-ABZ flight), IMO they are probably right, based on current caselaw, to deny compensation in this case if the cancellation of the AMS-ABZ can be justified by reference to extraordinary circumstances.