Shannon is a pretty well-rounded prospect, but it's surprising that despite his solid length and athleticism he virtually never blocks shots. Offensively he isn't setting the world on fire, but he's a pretty clear #2 option for an elite team, 58% true shooting, doesn't turn the ball over. Not bad.
I should also note that these rankings aren't positionally-adjusted in any way. It's typical for guards to be positive-impact offensive players and negative-impact defensive players, and vice versa. If you classify Shannon as a SG, his defense is probably around average for a first-round SG prospect, and his offense a bit below-average.