Franky, in the past aircraft noise has been a significant issue in Federal elections. The incessant, high volume rain, and arrivals and departures after 2300 hours on Sunday 5 June were during an election period, one that ends on 2 July 2016.
Notwithstanding fine detail in any legislation or legislative instruments, public perception would be that the 2300 hours to 0600 hours nightly SYD curfew prohibits landings or takeoffs (except for designated freight and small passenger aircraft, emergency services planes and in three or so instances, early morning arrivals, the latter only for six months of the year and only between 0500 and 0559) between 2301 to 0559 inclusive.
As noted above, there have been previous documented instances where airlines did not receive the delegated official's approval and were prosecuted for such a failure, sometimes receiving a significant fine.
As noted by others such as levelnine, 'bad weather' is not normally sufficient as a (standalone) criteria for an approval to be granted.
Until the report is presented to Parliament - 'tabled' - no one but 'the delegate' (or public servants who know him or her) can say for certain that approval was granted. If it was, we do not know the exact reason(s) why, but these are normally explained in the report - and can be interesting reading.
Many of us who live far away from SYD might indeed consider it a 'fuss', but in the past it has been a concern that has been brought loudly and persistently to the attention of Federal MPs and Senators prior to various elections. They have typically regarded it as a mainstream issue that required addressing, which is why for instance there is a consultative committee.
If 'someone' in authority such as a Ministerial delegate made a series of decisions that turned out to not be based on criteria set out in legislation, then that would potentially be a serious breach of his or her obligations. If however the decision maker acted in accordance with the fine detail of the legislation, then everything would be hunky dory.