The AMCAS no longer specifies "after HS" if it ever did but the advice passed down through the ages has been to limit activities to things that started during college or that were continued during college. However, I think that there are legit exceptions to the rule. Certainly, there are tons of Eagle Scouts breaking the rule every year. Anyone who was an elite athlete before attending college would not be chided for listing national competitition and I think the same can hold true for research. You tried it, were acknowledged for your efforts, and found you preferred a different type of activity in college. No problem. List it, particularly if you won awards.