Agree with OP's point of view to a certain extent. CX doesn't show the booking class until the flights are confirmed and you are on your way to the payment page. And here they only show the asia miles you can earn.
In order to see whether club miles or club sectors are applicable, you need log into the manage booking>My details>Frequent Flyer.
I would however thought that the OP, being Diamond status, would be aware of the various CX booking classes and the "benefits" that comes with each booking class !