"The debate should rather be whether we can really count any season in Sydney as winter!"

Good point! I was in Sydney 2 years ago, in late May - early June, during what should have been the beginning of winter. That didn't stop me from swimming on Bondi Beach, nor from taking my very first surfing lesson. True, it was a bit chilly, but certainly not cold enough to keep me off the beach. But one of my most poignant memories is looking at a clear, starry night sky, and not recognizing even one constellation. :-)