This one is actually able to be explained with bugs that exist in BF4. In the clip, he is at a large height advantage compared to your player, and the smoke. For some reason, when you are above the smoke looking at it in ADS, the top of the cloud often renders in as mostly see-through and clearer compared to those looking at it from a lower altitude. I observe this a lot on the more vertical maps, such as pearl market & metro (top floors of the buildings with smokes in the streets). I am not sure if this is due to lower settings, or if this is a common thing that other people have seen with their in-game settings, so it is not a bulletproof explanation, but one that I think is completely viable.
Looking at the round statistics, I am not seeing any signs of foul play/high KPM/high headshots %