I'm not one who has pumped HB. In fact, I have recently said that I like Salter's potential a little better based on what very little we know.
However, what I do STRONGLY suspect is that HB is a much quicker decision maker than JG. JG didn't "take a beating" last year. He took the longest of ANY SEC starter to deliver the ball... UT was mid pack in pass protection stats.
Blaming the OL has always been the "go to" for folks who do not want to see JG's very significant weaknesses.
UT isn't going to beat the best teams on the schedule without a difference maker at QB (positive difference maker). JG hasn't been that over his career. He doesn't anticipate throws well. He doesn't make post-snap coverages quickly enough to take advantage of openings. This shows up in his red zone passing stats and UT's red zone performance with him at QB.
JG was outside the top 100 nationally in passer rating in the RZ and 13th in the SEC. That's simply not good enough for a RS Jr with weapons like Callaway and Jennings.
cfbstats.com - 2019 National Player Leaders
cfbstats.com - 2019 Southeastern Conference Player Leaders