The Qantas Domestic QC lounges (and to some extent the Domestic Business) lounges are very different to UK/European domestic. They are large and very busy lounges, the Perth lounge in a morning is full to the brim of Hi Vis wearing Fly In/Fly Out workers in boots, and this is still accepted because they bring in a lot of money for Qantas (<2 hour flights with AU$1000+ each way tickets). These guys are required to join on site in uniform.
The Qantas Club elsewhere is probably where the improperly dressed issue has arisen, because QC can be bought or is provided as a perk from employers and perhaps where the dressing down occurs. A colleague of mine arrived at Perth QC in thongs last week and was given a pair of a rubber shoes to wear.