i don't see how anyone that watched judge play a fair bit could consider him outstandingly athletic for a high-major college basketball player.
It's because, given the way these people are using the word "athletic," athleticism isn't measured on the court. It's measured in units like inches and seconds. For you, it seems more like "good athlete" simply means good basketball player. In that case, he's not a good athlete trivially because he's not a good basketball player, right?
There are also further distinctions to make. You can imagine someone with more basketball ability than anyone else in the world (whatever that is) simply not being interested in playing basketball. You can shove him out on the court, but if he doesn't try due to lack of interest, he just runs up and down and doesn't appear to be a good basketball player and maybe isn't one. Isn't something like this the best explanation for Judge? He quit. How much interest can he have?