While we may choose to be contemptuous of bureaucrats in Canberra, we're in Oz so the laws of Oz apply. There are many who have been prosecuted over what the law actually said, versus what the law was meant to say.
So, to answer the original question:
20.7.1B 4.1(a) states that TODR and ASDR must consider "aerodrome elevation, ambient temperature, wind component along the runway, runway slope and runway surface conditions ..."
20.7.1B 4.1(b) states that the climb requirements ("segments") must consider "either ambient temperature and aerodrome elevation, or approved declared conditions"
Therefore the answer is: "No, runway slope is not legally required to be factored in to first segment climb through the application of CAO 20.7.1B"