I'm sure Danny knows who he'll choose as his number one pick IF he keeps the pick. He must have sent advanced scouts out during the NCAA year to evaluate players, knowing full well he had a shot at getting the number one pick. He'd be incompetent if he didn't.
IMO he's looking to see who he likes if he trades down. Being Danny he's thinking maybe he can get a top PG in this deep PG draft, and maybe a big at the same time, by trading down.
He can always have Fultz come in workout, and have a good measuring stick to evaluate from because he had other top guards come in for workouts. If Fultz is in fact, a star in the making, he should stand out from the others.