This is actually not a good thing.
There has been a whole lot of press in 2016 about how unis have "rorted the ATAR system". Perhaps some of the unis have offered places in a non-transparent way.... but many unis have been quite open. UWS gives bonus points for residents of western Sydney. UNSW gives bonus points for good HSC performance in relevant subjects and for leadership skills. It is all published. USYD seems to keep its cards closer to its chest....
If everything is in the open then people know exactly where they stand.
Why not publish interview scores? You can bet that the unis keep records of a quality that if someone challenged an outcome in court that they could defend themselves.
I personally don't think it is a good thing either to keep your admissions data
this secret to the point where you purposely have conflicting data from your staff that interacts with the public (at least be consistent).
However, my experience with this from the other side is that if you do end up publishing your minimum scores for entry you will end up with the following for your admissions staff to deal with:
1. Students calling who missed out by one point in UMAT or ATAR asking for leniency trying to state that they are competitive because of whatever reason
2. Students (or parents) misinterpreting the cutoffs - for example, especially at a university which weights both ATAR and UMAT such as Monash, if you release the fact that the lowest non-rural standard UMAT was (say) 170 and the lowest non-rural standard ATAR was (say) 97, then you'll get a whole lot of people who call up who got above 170 and who got above 97 ATAR and who didn't receive an interview (and correctly so), because if you had a UMAT of 170 you needed an ATAR of 99.95, and if you had an ATAR of 97 you needed at UMAT of 250. Given that universities use models that rank these students on a continuum (see: combined z-scores from the UNSW system) it's not feasible for the university to publish each ATAR vs each UMAT required for that ATAR. Other simpler but still stupid things might happen, such as (in previous years) students calling up with 60%ile UMAT when the minimum required for their UMAT was 60 average raw mark. This simply creates more work for the faculty with literally no advantage for them.
3. Even if you are a university that goes by a threshold umat cutoff (at least until ATARs are released), if you publish the one from last year and your cutoff for this year goes up by ONE POINT you end up with a whole lot of people calling and complaining that it wasn't fair because they made last year's cutoff but not this year's.
4. Any of the above may lead to legal battles between disgruntled students (or rather those students' parents) and the university which takes a stupid amount of time and money as well, and (except in rather exceptional cases) always results in the university winning. Yes, the universities do make mistakes, but they would usually be corrected if the student calls up with their scores above the cutoff for interview, and these instances rarely if ever progress to legal battles.
Universities have very good reasons to keep their admissions data quite secret - it saves them lots of time and money and means they can use that time better for all the students involved. It also means that, especially for universities which have other non-numerical based admission requirements, such as the JCU application form, that they can stop students from knowing exactly what they are looking for and thus gaming the system (and actually get the students with the qualities they are actually looking for).