They have looked at it as much as they could, they call the system pawn-to-pawn physics, a little blurp about it on this page: https://rainbow6.ubisoft.com/siege/en-us/news/152-303559-16/dev-blog-ping-abuse-peekers-advantage-and-next-steps

In general this is an almost impossible problem to solve 100% with the latencies involved in network play. They have made it especially hard on themselves with the one-hit kill (knife) purely based on position. If you want to know more i'd recommend reading this cool piece on the source engine networking. I'd really gives you an appreciation on how much of network multiplayer is actually tricks and magic to hide the latency, instead of the hard reality you seem to be seeing on the screen. https://developer.valvesoftware.com/wiki/Source_Multiplayer_Networking