Originally Posted by
skimthetrees
I believe this is because AA routing rules do not allow it. As a general rule you are not allowed to transit a 3rd region on one award. There are exceptions but transiting HKG to go from North American to Australia is not one of them. You can find a lot of blog posts on AA award routing rules that go into more detail. You can piece it together with two awards unless the segments are married segment restricted.
What you're saying is true however nowhere did the OP above suggest they were trying to go from NA>Australia via HKG, only SYD-HKG.