The reason he's ranked so low as a pure Wide Receiver is because he's raw / unrefined as a "true" Wide Receiver. Didn't get a lot of true WR reps over the course of his career.
Explosive, fast, good after the catch ability.
But he lacks polished Route running technique, and him switching to Wild-Cat QB although honorable to help his team.. hurt him a little as a WR prospect as it took away reps he could work on his craft.
He could be an interesting gadget player but ultimately I still think he goes Round 4, maybe Round 3 at the earliest because of his lack of polish, and what is his true position question marks?