We keep seeing these cool decklists and every time i see something like that i try to figure out the philosophy behind it.
4 Supporters: As long as you get the resources you need by other means, such as Victory Medal, Dual Ball, Energy Search, etc., you don't need supporters. The deck is CMT because it's fast enough to get the edge on Vileplume.
No Junk Arm: Four spots can be a lot and you sometimes have to discard valuable cards. Instead of Junk Arm, you can put in one-ofs or cards like the aforementioned Victory Medal. These cards may keep the opponent guessing, have them preparing for something that will not happen, and leave them very surprised. I think when the guy said he played no Junk Arms, people said, "WHAT? This has to be a fluke!" just like a lot of you and he was able to use the surprise factor to his advantage.