You know what, I took back my disagree. I still disagree, but to a lesser extent. I don't think you have to have used it, but I think you have to be competent enough to use it in a real situation.
As a point of story - my Mom, a white belt in Hapkido, went to visit her family in another state. My cousin is a police officer, and she wanted to show him what she learned in Hapkido. But he's not the type of person who is like "show me what you learned, that's really cool." He's more the chest-thumping point-and-grunt type of a guy. So he wanted to show how he was better than her, even though he's twice her size. She wasn't able to make the techniques work.
I share this story, because while I may consider her a Martial Artist because she's training an art, she wasn't ready to demonstrate the technique on a resisting opponent. She wasn't at that skill level yet. And it's not any indictment on her or the training. She simply wasn't there yet. At that point in time, she would not have been capable of using the martial arts in a realistic setting. With more training and experience, she will be.
So like I said earlier: context. In my opinion, and in class, I would call her a martial artist. But if she wanted to prove her hapkido skills to someone outside of the school, I'd caution her against it, because she's not there yet.