We have a very limited amount of space for statements in close reasons - if we could fit other OSes there we probably would but we are out of space in that reason's length to do that right now. We have space for only 69 characters more on that close reason - if we expanded to include eOS and others we wontwon't have the space to include them all - which is why we simply say "This is not Ubuntu" and point people to U&L for other Linux distros (Mint, eOS, etc.)
