The main reason Jamie has given on discord is due to the view range and the advantage this can give to players using larger resolutions being able to see more of the map.
Seeing more of the map then lets you navigate through caves easier, as you can see what mobs are coming. It will also allow you to see other players coming to you sooner allowing you to escape/gank easier. Would be quite a big advantage for those with larger resolutions over people with smaller ones.
He could support the larger resolution, but then not draw any mobs/players outside of the standard view range (like his ghost cave on marble), but that would negate the point of allowing larger resolutions, and probably look quite daft without a fog element to it.