I coach in Arizona and have watched plenty of film on both, Rattler is an elite level QB and the best to come out of Arizona in the past decade, Conover is the second best I have seen in that time period and just a tier below Rattler. Also, Rattler was going against another Freshman as his primary competition last year and Conover going against two more experienced QBs with much more game experience than Mordecai had at Oklahoma.
And obviously Hall and Romney are not better than Rattler, neither is Conover, but he will be a high level college QB, there was just no need to rush him with two other viable options and he was making freshman mistakes in camp, which if you watched Rattler last year you saw him make early in the season.