It seems to me that he has a really exceptional ear. He only has to hear a word a couple of times, and he's got it forever. And these aren't easy languages.
But he also has his own theory for language-learning. It certainly works for him. Would it work for us?
I doubt it. I speak fluent Italian, and I'm told I handle verbs impeccably. Like Xiaoma, I didn't study it. Which is probably one reason it took me three years to become even moderately fluent.
I'd have been pleased if it'd only taken a week or so.