Still dont know how you are getting that, when I check classic availability I get: "Trip from Sydney to Hong Kong is not available on the 17 Jun. Alternative dates can be selected below." using an SG account. I wonder if your looking at cached content, and not what others see?
I don't know, I do get this availability from different computers at different locations and different QFF accounts (My friend and myself).
Anybody else can see this availability?