a large percentage of the accepts in dec are md/phd [30%]
the other students who were accepted in december were a combination of early-submitting and 'high-achieving' [whatever that means] students that cornell wanted.
[un]fortunately the yield for both groups should be lower than the the average yield for the school - chances those students have other great options to consider as well.
this is speculation, but i imagine that a bulk of the matriculated students will come from the march batch. if you have q's about the place, feel free ... goodluck.