And yet a Ural can? In think you are confusing a willingness to make an engine emissions compliant and the ability to do so. Compliance just means a drop in HP. There is no reason a R1200 can't make the cut but it would also drop in HP. It is not a technological issue.
It is why ducat went from a 600 to a 620 to the 685 while hp stayed more or less the same.
R1200GS has a marketing problem. It needs the boxer engine for the history but has to compete with the HP war as the bikes become less adventure and more tourer. It is hard to compete against Ducati, Triumph, etc and drop HP especially when these bikes get less and less off road capable.
Any mfg that is claiming they "can't" make an engine emission compliant should call URAL.