I'm looking through AT GEN 65 (fire extinguishes) and all it says is for charter you have to have one unit installed to the pilot compartment - not that it has to be reweighed every 6 / 12 months.
The only reference to the AWB is:
Note 5: Airworthiness Bulletin 26-2 provides advisory material.
The AD isn't forcing you into using Australian Standard as the maintenance program.
Guidance and advisory material, as such, is not legally binding however prudent it may be to adhere to the recommended practices set out in guidance and advisory material, such adherence is not obligatory under the legislation.
Haydn