Yea I know it's ridiculous here, but the thing is that you never run out of map, you know how in every open world game at some point the game tells you that you can't proceed anymore because you've reached the boundaries?
Than here it never happens, game is always "building" terrain for you even if you are out of the map's boundaries, you will just drive a big and empty space with nothing to do but you can do it for hours if you wants, that's what I got from them.
I think, not sure, that this is why the pop up is so bad, this is how this engine renders, but wait for someone more knowledgeable to clarify, maybe I'm talking nonsense,