I think I am. As a simple example, Chris, who I would say is probably the second best, lost to some random Snake with Yoshi at Neumont, I played that same guy later that night and 2 stocked him. Chris also loses to a lot of people as Yoshi that I dont lose to, and the people I do lose to, he loses to even worse as Yoshi. Utah tbh is pretty ****ing terrible when it comes to playing as Yoshi. The fact that I can solidly say Im the best Yoshi is kinda sad cuz tbh Im not even that good.
Also, just to point something out, saying you're best with a character just because you are better at one MU is just dumb, It would be like saying Lada is the best ROB just because he's probably the best ROB in the Sonic MU. While it's true that Kevin is in fact probably the best ROB there is for fighting Sonic, he is without a doubt, not the best ROB there is in general.