I reckon the stadium managers decided that if four gates are required for 40,000+, they could get away with three gates for 30,000 - which was probably what was expected for on a day where rain was forecast against a team on the bottom of the ladder on the Sunday before the school holidays.
Then 43,000 turned up, which surprised me a bit, and I bet it surprised the stadium managers too. So then they opened the gate to accommodate the larger-than-expected crowd. I realise that for those that turned up 40 minutes early it might have been annoying to only be in your seat 20 minutes before the game, and look forward to the outcomes of the Royal Commission.
Dead set, there are much bigger things to worry about. Like the footbridge not being ready yet. It took me an entire extra 15 minutes to walk from the Royal. Sometimes I lie awake at night wondering about the pint I could have had.