I doubt that the 1988 "word-set" survey (I'm not sure what its official title was ... ) would pick up a 'stray' new phrase. The aim was to find out the regional variations in day-to-day usage for a set of familiar objects. This could then be extrapolated to see how the distribution and interchange of such terms fitted into the Australian settlement pattern.
Why I mentioned it was to highlight its discovery of the distinctive "Sydney Triangle" region ... and to suggest this particular phrase / usage might be, more or less, confined to here. I didn't delve too deep ... I have a magazine issue looking just as late as it always does and I just put the theory down - as much as anything - to remind me to look more closely ... when some of the 'spare time' stuff happens!
I would be very interested to hear what Barbara Horvath has to say, from the 1988 project. It's not aimed at solving this query - but it was a good, valuable, project.
BTW: The bushfires that cut our north of Sydney road and rail links affect quite a few of my colleagues ... but I walk home, in the inner suburbs, so I just have to withstand the heat ... and envisage something cooling and tasty at the end of an hour's (hot) walk!