not sure about 'dropping bar' comments on the CASA side as I've not studied their theory, but myself being in the EASA theory system/training now, I can see the reasons behind.
I'd say the at least unilateral acceptance/validation on CASA side may be partly due to the pressures of operators and MROs asking for qualified engineers from abroad. It's been more than a year, maybe two, since the aircraft maintenance engineer job qualification has been put on MODL, special demand list, even Critical Skills List within MODL- these get priority processing and extra points in the whole immigration to Australia business.
After going through the hurdles here, some, especially more senior engineers may be reluctant to try out Australia due to hoop-jumping paperwork.
Technically, there's no need for agreement, if it's unilateral, as CASA can publish anything they wish about them accepting EASA licenses, isn't it?