A few pointsTerminating at Western Sydney Airport is a good idea - in the sense that it puts the nail in the coffin of the 'true' HSR dream and promotes discussion of Medium Speed Rail alternatives that do not prioritise more time-sensitive sensitive portions of the travelling market - such as business-class air travellers - to the detriment of overall project cost. If terminating at Western Sydney Airport was combined with a reasonably fast and constantly high-frequency metro service into the Sydney CBD it could be very competitive for a fair amount of the market - not all of it, but enough.
- If you run via Badgery's Creek, say good-bye to be competitive with Syd City to Mel City HSR vs Air. It will add 15-20min easy to the trip and likely many billions of dollars.
Alternatively the European model of using existing conventional tracks for inner-city station access and high-speed segregated routes outside of that could be considered in this context as well.
I agree with you that promoting the Badgerys Creek 'Aerotropolis' as an international hub for airlines is onanistic.