If you could learn what ward skin your enemy is using, could you know who just warded from over the wall and thus know the position of the jungler without really seeing him?
Or is there a protection in game so that you can't know who exactly warded?
Here is a situation where this could be useful:
You see a ward that has just been placed in your bottom river bush. If it's the jungler, you can know that your jungler can invade top side and not meet their jungler there. If it's midlane that walked down and warded, you wouldn't be able to guess the above.