Hard to disagree with that statement. You're right, he will benefit from spending some more time in the D-league. Regarding his defense, it does look like he is a bit slow laterally. From my minimal exposure to his highlights, it appears that slow lateral movement also for guards to get by him fairly easily... but he makes up for this with his length. Im rooting for him.
I’d love to see him continue to get better and have a shot with the Rockets. Not expecting to see it, but with his measurables he’d be an asset if he improves.