Anti-rushing system

Hi ...i want to tell you something that astonished me about the anti-rushing system in L4D. I am usually playing on the last client but i get warned many times a day that i am rushing...i thought rushers are in the first-second-third client and not in the last one...In addition i have seen many rushers who didn't get the penalty and teleported to the last client for rushing...so i think that sometimes anti-rushing system just failed :|