If your manipulating a game to get an outcome (keep the scoreline close) is that corrupt?
Only if it is done unevenly.
If every game is made close by the refs, in the same manner as every other game, then it's just a part of the comp that all teams have to deal with.
It just means every team needs to be setting up to play their best footy in the last 10 mins to win the grandstand finish. And goal line defense becomes the most critical aspect of being the best footy team, so you can defend against all the catch up penalties when you're in the lead.
One thing I will say is that it gives the refs a lot of cover that they can manipulate games under. If everyone is expecting the refs to bend the rules, because reasons, then when they bend a few rules to swing a game unfairly it's much harder to spot.
So all in all, the refs playing catch up is great for getting new fans into the sport, as there are more tight games, but it makes the game ultimately unsatisfying for the long time fans, as it makes the refs actions very predictable and boring, and it even leads to some fans going a little crazy.
It reminds me of a doco I saw about Scientology for some reason.