COVID: The shape of an emerging outbreak?

The current situation:

Australia nearly had the virus fully under control, with little to no community spreading left.  Until.

Unfortunately, returning travellers were isolated for 14 days in hotels.  Not a problem in itself, but in Melbourne hotel-based enforcement was contracted out to major security companies, who subcontracted it to subcontractors, etc, resulting in non-professionals being recruited by WhatsApp, told little about the gig, and put on at short notice with scant training.  Everything went to pot from there.

Melbourne is now trying to tamp down a full-fledged outbreak, where new infections are hovering around 400 per day.  Despite the border closure between Victoria and New South Wales, infections have leaked through to Sydney, mainly via the road transport industry and Sydney pubs.  Yes, the border is a little too porous, and Sydney social distancing enforcement too lax.  Sydney infections today: 19.  We do contact tracing, and nearly all those 19 are traceable to one of the clusters.  So far, with a handful still under investigation.


In that context, ABC (the Australian Broadcasting Corporation) has in the middle of their daily coronavirus briefing included an interesting graphic of the cluster origins:

It's not easy to fathom the cause of the differential in cluster origins.  Melbourne's pattern may be due to a more mature spread pattern, and Sydney's pattern's possibly reflect the way the outbreak is emerging (Sydney's clusters include a gym across the road from one of the pubs).

But I haven't been able to fathom why Melbourne's clusters don't include pubs and restaurants.  The regulatory environment seems to be rather similar, and Melbourne people are by all accounts behaving as incautiously as those in Sydney.  Pubs in particular are great disinhibitors, so why is it not so in Melbourne?  Answers, please on a postcard, letter or emails.

I recommend the above ABC daily briefing.  Meaningful insights often emerge.

Update 28-Jul-2020
Five days later, the cluster picture is not significantly different, apart from some relabelling:

For Victoria, Retail remains a minor source, while pubs and restaurants still don't figure - that will not change, since they are now in lockdown.  The Hotel source in Victoria was the location at which overseas returnees were isolated, but contamination spread via security guards.
It must be stressed that this represents identified clusters, and doesn't include single or unidentified sources.  However, Victoria has hundreds of cases per day dating back a full three weeks whose source is still labelled "under investigation".  NSW is still hovering around 10 - 20 new infections per day, most of which are traced to source.  Because our tracers currently have a manageable load.