I don't understand how Sydney had to quarantine just because of an Adelaide stopover but we had a barrage of people from New South Wales coming into Victoria a couple of days ago and no requirement to quarantine. This just does not make sense.
Each state reserves the right to enforce its own border restrictions. WA's are probably the strictest in the land. Their risk categories are based on figures such as number of days since the last community infection and average cases per day. SA is in the second-lowest risk category, but WA still requires SA visitors to observe a 14-day self-quarantine period.
Syd was at Adelaide airport for a few hours. SA locals possibly joined the flight in Adelaide. All passengers would have been required to observe 14 days of quarantine.
Victoria's border restrictions are simply less strict than WA's. You can form your own opinion on that.



