I noticed the same thing, only because I played the position my entire life and did the same exact thing. Mine was because my hands would be sweaty so right before I went to throw the ball, I'd spin it to get the "dryest" grip possible. I never noticed him doing it before, so I'm wondering if it's just because the ball was wet and it was raining? But funny you mentioned that, I saw the same exact thing and thought "Oh wow, that looks familiar" LOL.
I had coaches who yelled at me about it, but it really never impacted me that I can remember. He's still pretty universally praised for his quick release, and he started 27 games in the SEC that shaped that opinion. I'd think if there was a hitch consistently for him to spin the ball before it came out and it impacted his time to throw, it'd have been noticed and discussed by now. I also had coaches yell at me because if you're blindsided "mid-spin", well........