I am an advocate of learning some medical terminology, so I'm definitely not against learning before the fall. But I'll tell you why people will say you shouldn't study:
- You will soon be studying so much that it will consume your life, so enjoy your free time while you still have it.
- Medical school is a 10,000 mile race. Since you don't understand the pace, your pre-study will amount to a 5 or 10 mile head start. In other words, you will NOT have any meaningful advantage compared to someone who doesn't study anything (and possibly a disadvantage if you aren't as fresh from relaxation).
- You don't know what to focus on, therefore your studying can be largely inefficient.
I think those are the key ideas. That is why I would advocate medical terminology, as learning words is something that will be easy to retain and will not take up much time. Studying any rote memory material is worthless because you will not retain it.
Conclusion: Do what you want, but realize the risks and consequences.