That would have been unprecedented. Remember that the 1950, 1951, and 1953 proof sets were all CuNi. Yes, it would have been nice, but the RM couldn't anticipate the kind of nostalgia that's around now, nearly 50 years later.
As Rob pointed out, that's a circulated example and has lost its proof coating and become just an ordinary 'impaired' proof.
No, there are not different kinds of proof out there, it's just that they introduced frosting in the early 80s, and before then it's a bit hit and miss. Your Aussie set doesn't look any more frosted than your 1970 set, except for the bronze. You can see frosting on the relief of all those 1970 CuNi except the sixpence.