The problem DTL is that you assume that having the title of the Best Pika and the Best MK guarantees that you are the best at that matchup, when this is not a guarantee or even always a strong possibility.
It's safe to say that Anther is almost certainly the best Pikachu player at that matchup. I think he has clearly shown this, and he also plays a lot with a top MK (Judge) in his area. M2K, on the other hand, doesn't have any **** Pikachu players for him to practice with, and you could reasonably argue that someone like Judge potentially knows the matchup better than M2K does.
The believe or thought that two of the "best" mains of a character knows the particular matchup the best is not a guarantee. Take me for example. Setwise, I am positive, with Wario, against every top Marth player I have ever played. Now, just because I beat them, does this mean the matchup is in Wario's favor or even? Hell no. Just because I played really good Marths, does that mean they know the Wario matchup the best out of everyone? Hell no. In Fact, I have had more trouble gameplay wise with some of the "not as good" Marth players who happen to understand the matchup better but as players are not as good overall.