Don't kid yourself, Gary . . he struggled mightily, but, finally got there.
Billy, you and I have butted heads over this before, but I'm always happy to have a civil discussion, so I'll lay out what I stand by on this subject and move on.
Marcus also struggled (as all freshman PGs do here) when he was thrown into the fire, and Joel would've certainly had bumps as well had he started. To use your term, Marcus "got there" and was good by the end of his first year, and excellent as a Sophomore --- and since JB was as ready for that job as any freshman who's ever come through here, that would have been his trajectory as well.
Our starting lineup was dysfunctional in 2014-15 because Paige was the only legit Guard on the floor (not to mention the only 3-pt threat that scared anyone and the only credible ball-handler), and consequently poor Marcus got the crap beat out of him physically while opponents packed it in on our Bigs
When Berry would come in everything immediately changed for the better for two reasons: 1. Now there were double the ball-handlers and outside shooting threats (and thus better spacing), and 2. JB was already very good at being a PG and Marcus could play a helluva mean 2. JB and Marcus were often magic together from the get-go (size be damned) and nearly always kicked our offense into high gear... and of course that was the backcourt that would lead us to the Final Game the following season.
Fact is, Joel didn't go through some magical transformation after his freshman season. He came to Chapel Hill as ready as one can be to run this system, and given the opportunity would have done just that as a starter, albeit taking his lumps (just like every frosh PG who started from game-1 did, from Phil to Kenny to Ray to Marcus) and come through with flying colors in the end, just like those guys did.
The only thing that not starting Joel that season accomplished was to merely delay the inevitable, and unfortunately kept that particular team from reaching its full potential. And although you may not want to believe this, I can tell you that was something that was quite apparent to some key team members and by February of that season became a source of dissension --- not from JB, but from teammates who knew how much better they were when he was on the floor.
But hey, that's water under the bridge, and now in 2018 we're obviously all thankful Joel returned for his Senior campaign, and who knows?... had he started from game-1 as a Freshman he may have already left, so there's that.
At this point, as a UNC fan I'm just gonna ride this season for all its worth while he's here, because the minute Joel Berry announced he was coming back we suddenly had a legit chance to do something special in the post-season again.