The problem with the distribution/DE divide is that there’s a lot that doesn’t fall squarely in the realm of one or the other, and so confining yourself to just

The problem with the distribution/DE divide is that there’s a lot that doesn’t fall squarely in the realm of one or the other, and so confining yourself to just being a DE means making a big pile of compromises and diluting the end product. I don’t know specifically what those things are in the case of elementary, but for example one could imagine certain bits of design in a desktop’s file manager being tied to how the distribution’s filesystem is arranged. Sure the file manager would technically work with other filesystem designs, but then the file manager may as well not exist because it brings little to the table that other file managers haven’t already. So I can see why someone who’s concerned with fine tuning details in the desktop experience they’re crafting wanting to also be a distribution. Unfortunately that’s also a massively tall order due to the time, personnel, and effort required to pull such a feat off.