Why would Jackson want to leave if his role remained the same?
According to Jackson, he left because he wanted more "a bigger role." A bigger role being larger and more important than the same role.
He was the starting 2 guard. Waters doesn’t make any sense.
I don't think that's exactly correct. Hill and Geno played a combined 71 minutes in the backcourt CJ's freshman year. Gray and Hamilton played 27 and 33 respectively. CJ and Ryan Williams split time 45 minutes at the three, 25 to 16. The next year when Hill got hurt Mason Jr played 30 plus minutes and CJ played slightly fewer than as a FR (24). That was the year Derwin Kitchen was declared ineligible (no doubt he'd have have gotten CJ's minutes) and Maybank got hurt. The next year Patterson, Wright and Calhoun all came in, all of whom were allegedly better shooters than CJ.
Which anyway is immaterial, since Jackson himself said why he transferred. Maybe he was lying to make Norm look bad although if Norm was recruiting over him and that pissed Jackson off enough to transfer he'd have no reason not make Norm look bad and neither would Waters for that matter. It might be that everyone's lying and you've sussed out the truth but I don't believe it.