Most civil ACD will issue "maintain x000" with initial clearance. Pretty much an international common practice. Allows TMAs to streamline departure procedures and ensure separation with other traffic in the TMA.
RAAF are a whole other group of anal retents and use the (MATS-correct) "amended x000".
SY DEP are instructed not to issue jets with a level below 5000 on initial departure. This came from a domestic 767 carrier mitigating a number of level busts. It is surprising Darwin use 3000. That's the RAAF for you.
Radio fail procedures place responsibility on the pilot to climb to lowest safe altitude.