I think it is an new feature in the epic game
Unfortunately for that theory, the diagonal shading does not coincide with the cultural borders in the screenshot. The cultural borders of the city are just visible (in green to match the cities flag) below the shading.I think the diagonal shading is just to make cultural territory/borders easier to see.
Quick side question:
When you say 'epic' here, do you mean standard game play, or an epic-length game? I've noticed that the descriptions of update refer to the 'epic' game, and have been hoping that's just a generic term for standard game play, not an indication that some updates will only apply on epic-length games.
Probably obvious, but just making sure I'm understanding correctly...
But why would archery units be given a distance mode? Wouldn't that be overpowered?