You're right. It can be the formal "you". I reported it, and told them it will confuse people later on if they say it's wrong. I don't know if they'll fix it or not, though. Hope so. I think it's strange that they don't teach the formal you from the beginning. Do they want us all to seem rude and overly familiar when talking to people?
While you are correct, what you are speaking of is when 'di' is used as a prepositional article. Here I believe 'di' is used as a partitive article. See this link:
I also thought vuole was you because i remember a native speaker asking (me) Che cosa vuole fare? Lol i didn't notice that DL never uses the formal. Di they use it in Rome? That's where I'm going. Is this program going to make me sound disrespectful when i try speaking Italian there?