I find it interesting that their concern is Marth.
I understand Marth has some of the best overall match-ups in the game, only with D3 and Snake as slightly disadvantageous match-ups disregarding MK. However, I fail to see why we would think Marth would dominate the scene. His many of his match-ups are 60-40, meaning they are indeed winnable, since I find that if a Marth makes a mistake, it is much easier to capitalize on it. I would expect his usage to soar since he is the safest MK alternative due to the nature of his match-ups.
However, I agree with EL in that other characters such as Snake, GnW, D3, Falco, etc. have certain match-ups where they wreck characters. We humans like to use numbers to describe, and the other tops have favorable numbers. I could see people instead maining and seconding an assortment of top tiers to cover match-up weaknesses and to wreck any character possible a more likely choice.
Of course that thread goes so fast I don't pay too much attention to it to be honest. Someone help me out?