Well there was no way the Armidales would (or even could) go that far south, in fact it was necessary to station frigates up north during the wet because the weather then was often too rough for PBs. The OPVs will be a massive improvement over the PBs, freeing up a significant number of frigate sea days as it is so Southern Ocean ops, while a nice to have, probably isn't worth the extra expense and compromise adding the capability would require.
The AWD uses a different grade of steel (less brittle in extremely cold conditions) than the Spanish build ships specifically because of the RANs experience sending majors down south on rescue missions etc. Logically the SEA 5000 ships will do the same.