Going back to OP's post... I think it's admirable and even unique that you genuinely enjoy studying. I don't think a lot of people in general can honestly say, "I love studying in my free time." If what you said about your grades and studying habits are true, then obviously you are an academically gifted student!
But, I would say that all this only makes you a great student; and you are not going to be a student in school forever. You need to apply what you have learned and studied into real-life problems and matters (and having hobbies outside of academics can help this process, IMO). If you have this immense amount of knowledge in you, then why not do something with it? There is really no use in just accumulating knowledge and being the smartest student in the class if you are not going to do anything with it. Personally, I think education loses its purpose if people lack the abilities to apply it in one way or another.
So, a short answer to your original question is, no. I wouldn't list studying as a hobby. I think you can show your passion for studying and sharing knowledge with others by listing it as "Tutoring/Teaching." That's the extent to which I would talk about it. I really don't see a way you could make "studying" sound impressive to adcoms. Just let your transcript and MCAT score represent your academic success...