It's not exactly additional data. You can read more about how our patches work here.
So, you're saying because it's open world the patches are bigger. I mainly play open world games (GTA V, Far Cry, Witcher 3) and I have never seen any of those games tag so many huge patches in a row. Two days ago it was an 18 gb patch, yesterday it was a 13 gb patch and today it's a 12.5 gb patch. That's 43 gb of data in three days. The game itself is only 85 gb. I only have 250 gb cap. Maybe you should consider this before patching something. Many people who play your games have data caps. I love the game, but I can't keep downloading these huge patches. That's not even mentioning the 50 gb I had to install after getting the game to begin with. I have a digital copy on a 500gb XB1. This one game is consuming 1/5 of my hard drive space. I'm going to have to wait until next month to continue playing. I hate quitting a game halfway through. I have an 8 game backlog on XB1. I will have no trouble filling my time, just wish it was with this game.