I agree with your definition with one minor distinction -- sometimes, a "lead guard" isn't a big scorer, just an off-ball guard / wing with versatility and the requisite ball handling to chip in and spell or play the point.
That's what I think Dual might be, although I think he has upside.
Again, I don't have a great feel for his ability to lead half-court offensive sets, which is the true value of a point guard. I do think he's got some versatility. I worry that his handle might be just a bit too loose from the clips I've seen of him playing half court. In transition, I think he'll be lethal.
Also, a lot will depend on what type of offense we run. If it is a full out spread, then Dual paired with two versatile WGs will work, and it will minimize the traditional "need" for a point guard setting the table for everybody else. Lots of unknowns right now.
But I enjoy the point guard discussion, and your thought provoking / insightful post.