Yes, that’s the essential difference between redirect models and delegation models. Can exports implement abstract methods? My personal opinion is that we should resist the temptation of doing this, but am willing to entertain arguments to the contrary.
Just one observation: Once you accept that export can implement abstract members would it not be logical that you should also override concrete members? But that needs an override! So what should happen in this case? (I believe there is no good answer under the delegation model).