Several points (i'm not a ks cm, but I have friends who are)
A) yes there are people that will wait for their fp time and clog the fp return line. the cm usually tries to keep the area clear, some are better at it than others.
B) once you reach the merge point (where they collect the fp), you don't have to stay to one side or the other. you can go to either side. fp and standby are together. MERGE point. most people think they have to stay on the same side they were originally on. not true. if the other side is faster, go with it.
c) fp return is, without a doubt, the single most stressful position to work. Not always easy to keep your cool. sometimes the only way to make folks listen is to yell.