The positive case at the Playford hotel tested positive on 4th May and was moved the same day, which is also the day the Melbourne man was discharged.
Given they don't test inmates at the hotel daily, the Melbourne man could have been infected through aerosols before the 4th, although Vic seem to assume it happened on the 4th.
Melbourne guy had symptoms from the 8th, but you can be infectious before you experience symptoms so im not sure the claim that he wouldnt have been infectious on the ADL-MEL flight is a given.
Spurrier provided the dates in this article:
SA health authorities are investigating whether a man who was released from hotel quarantine — then tested positive for COVID-19 in Melbourne — acquired the virus while in isolation. The Victorian man was in a room alongside another traveller who tested positive to COVID-19.
www.abc.net.au