Hello,
I can understand the doubt this raises, knowing that at one time, in another game, some players could change the graphics settings of the game to make grass and certain elements disappear, which made the enemies that were hiding visible behind that.
But I'm not at all convinced that the advantage is so great with the graphics settings in BF4 discussed here.
It would become very difficult to discern those who do it for a performance issue versus those who do it to have an advantage. And I would also add that those who have a better graphics card with Ultra graphics settings have an advantage over others. They see more details and see further. There are also other parameters like FOV which can give some advantages. Add to that those who have a bigger high quality screen, better mouse and keyboard, etc. The list would be endless.
Since these settings are accessible to everyone in the game menu, I don't see why this would be considered cheating. It's not like it's a parameter to be edited in a hidden config file.