I think one of the most concerning issues here is that the ACCC is focussed on price as the lever. There are a number of other factors that influence consumers besides price - do they not get a look in? Competition isn't just about how much you can buy an airplane seat for!
The ACCC decision on VA/SQ can be found here:
Virgin Australia Group & Singapore Airlines - Authorisations - A91267 & A91268
And yes, it's broader than just price - the ACCC talks a lot about the value of amenities to business travellers beyond the price of the airfare.