Roy's a grade A fraud, but I don't want to get into that because that isn't what this thread is about.
The 2/3 thing is meaningless for a variety of reasons. First of all, as has been said, at most places there is very little difference between the 2 and the 3. Offensively, there is no difference at all at most places. And defensively, the 3 tends to be the bigger guy and the guy who is better on the boards, which would be Barnes at any of his possibly 6 destinations.
Realistically, he isn't going to play the 2 at Duke (even though K doesn't label positions) because they have Dawkins, Curry, Smith and the need for a SF. He isn't going to play the 2 at UNC because they have Strickland, McDonald, Bullock, and the need for a SF. He isn't going to play the 2 at Kansas because they have Taylor, Johnson, and the need for a SF. Harrison understands all that, he's an extremely bright kid.