As I've posted before, I always think it's important to try to distinguish between what you know and what you don't know.
With Kupp, a rookie WR, there's a lot we cannot know. Will his skills and competitiveness translate to the NFL? Now way to tell about that. OTA feedback has been positive, but it's pretty weak evidence.
I do think, however, that we are beginning to know that Kupp is a very smart player and is locked in to learning the offense. We've had a LOT of comments from various sources on his football IQ. I don't think it's premature to begin to figure that as an emerging known.
And, IMO, the head is a very important component of a good player's skill set. The very best players always play smart. Game IQ (not to be confused with other kinds of intelligence) always raises a player's performance and ceiling. Similarly, many a transcendent athlete has been held back by lack of it. Think of Quick!
As a Ram fan, I think of really smart Rams. Ike, Warner, and, especially, Marshall come to mind. Marshall was legendary for his mastery of the entire game plan and his ability to turn a coach's level of awareness into performance.
Is Kupp like that? Maybe to some extent. I doubt he'll be able to use his brain to dominate as Marshall did. But, I'll tell you what, it's hard for me to imagine a reasonably talented WR with remarkable game intelligence who busts out or fails to be productive. He may or may not be a star, but I'm beginning to expect him to make us glad we have him.
For me, intelligence is very important and I don't know that we have to wait until the season to start figuring that Kupp has it. I think it's enough to begin to hope in the guy.