Just going to reiterate what Drew said, and I've explained this to you a while ago. It's the same frames per second, but you are traveling a greater distance. The more people going fast the more the engine has to keep up with it...the more frame rounding and general BS. It creates an illusion of lag and the engine can't handle it. There's a reason lightweight got the nickname "crack head pro".
P.S. If there is actual latency or lag then it will make it worse, too. A player moving normal distances per frame in lag will only be slightly ahead, but a player moving farther distances per frame could be a whole hitbox ahead.