MMC is that size of a "feature of size" (FOS) where the most amount of material is present for the stated limits of size.
So, the length of the radius feature has nothing to with the allowed position tolerance as the tolerance by default applies to the entire length, depth, width, etc. of the feature.
Without an image showing the feature and the size/tolerance specification a full evaluation cannot be given. I'm not sure from the description that the position tolerance specification is even most-correct. I suspect that a Profile of Line or Surface may be more appropriate.