I do like Coach Nick so I'll have to take his word on some of this.
One thing I can't agree with is that his argument is that most of the NBA uses a dropback defense so that would given Ball plenty of room to put up a floater because the rollman defender will drop to the rim. That's absolutely not true, the Bulls were one of the last dropback defenses last year (and one of the worst overall defenses in the league because of it) and even we switched to hedging this season. It's very standard now to not allow ballhandlers open looks on the perimeter, and why the ballhandlers in the NBA that cause problems are off-the-dribble pull-up shooters like Trae or Murray or Booker. There are still guys who are primarily driving threats but they all come with stupid athleticism like Morant. The Westbrook/Wall style of point guarding is becoming more rare...and to this point hasn't actually won anything.
I do agree that like his brother, he can become a spot-up catch & shoot 3 point shooter. But being a non-threat off the bounce limits his ceiling quite a bit as your best player, so on a must-score play Ball is hanging out in the corner waiting for a kickout 3 from someone else making the play.
All this is mitigated by this being a weak draft, everyone else has serious question marks as well. What probably was most interesting was that Coach Nick thought his off-ball defensive awareness was very good, that his body language shouldn't be used to measure his defensive capability. We've seen that non-shooting PGs with great vision/passing and great defense can work; eg Rondo, Mavs era Kidd. But if you're missing 2 out of 3 (shooting, passing, defense) it's tough to win with that PG.