Sometimes I wonder if some college coaches get away with buffalo-ing the umps!
I imagine it happens.
I know for our HS games, I'll sometimes do some completely legal stuff using the DP/Flex with moving people into/out of various defensive positions, and I've never had an umpire actually make me show my work, so to speak.
Had a situation yesterday where I was moving 1B to P, P to the bench, and a girl in the lineup/on the bench (technically not the DP) to 1B. All 3 girls were in the lineup and staying in the game. The Flex was the 2B, who never left the field. The ump just asked about subs, I said no subs just moving players around, and he accepted it without bothering to make sure. And that wasn't even particularly complicated.
I assume most college umps are a little more attentive, but I'm sure that's not always the case.