Of course UNSW has restrictions like this - it has a UAI cut-off, no? Whether UNSW has an intake of 10, 20, or 100 is immaterial and shouldn't worry you, because you can't do anything with that information. For example, if there are 10 places available, and 9 have been taken, how will you get that last place? By getting a high-enough UAI so that you're 'next on the list', nothing else. You won't even know how many slots have been filled up anyway. If you are interested in getting in the course, worry about getting the right UAI. For USyd, it was 98.95 last year, and for UNSW it was 92.
(FYI the intake for USyd is 20, but the same could be true for UNSW - it might just be a less popular course, so they lowered the cut-off UAI).