Less than 30 innings pitched is an absolutely ridiculous number. We had 2 pitchers that weren't starters than threw more than 30 innings. Marsh wasn't upset that he didn't get over 30, that is just silly. He was likely upset because he was disrespected and used poorly and in a way that he couldn't succeed.
As for Hill... he had 94 at bats. That number was under 100 because the UK staff jerked him around for the better part of 2 months and only allowed him to pinch hit. So while PT was a factor, it was more that he lost his starting position despite never being told he was losing it and despite the fact that he had an excellent fall. He was hitting over .270 when the staff sent him, without explanation other than 'we're giving you a rest,' to the bench. This after just 8 games. Then, others like Rhodes and Estep were given chance after chance and were not removed from the lineup despite struggling as much, or worse than Hill. Not to mention that the move harmed the team defensively to such a degree that the pitchers had to essentially revolt to get the staff to change the lineup. So, while PT was certainly a part... there was a whole lot more to it.