So I recently bought Forza Horizon 2 and after a while when I was standing still with the car I noticed how all the shadows were moving very choppy. And once I saw this there was no way to not see it. So if you are reading this over at Turn 10 or Playground Games, I really hope you’ll patch this because it is very annoying once you’ve seen it. It kind of ruins the entire experience.
It’s a part of the in-game experience, I saw this too when I play this game 
When you start talking about forza horizon 2-graphics you end talking about xbox one-gaming/hardware-performance - this does not make sense, because everybody knows this issue.
I’ve noticed it as well, maybe they couldn’t get the sun to move smoothly so they just left it as is. It’s not a deal breaker but it is kinda annoying.
Having the lighting engine render the ever-so gradual movement of sunlight and the subsequent shadows, presumably, would be too taxing for the console hardware. Instead, the sunlight moves in increments which causes the shadows to move as such.
Part of the reason u notice this also is because horizon only runs at 30 frames per second.
Horizon could run at 120 FPS and with the player’s vehicle sitting in place you would still notice the sunlight moving in incremental fashion. In this case, it isn’t a matter of frame rate; it the result of sparing processing power wherever possible. In short, Horizon’s daytime transition doesn’t happen as it does in the real world (the rate of transitions aside); it is occurring just as the ticking second hand of a clock does. Tick. Tick. Tick.