I don't think so.

I did 3 in the same morning, through different ways. I don't see they fight with each other. And, my case got approved within the same day.

Think about this. The staff in NSC must be very busy. Even they want to help you, they have so many case in their hands and they may not have time to help. So, getting attention of several people there may help. If one doesn't have time, another may have. Who knows.