Procedures in AFM
The Airbus AFM and FCOM both contain passages similar to the one Bloggs posted above.
Airbus AFMs do not contain Standard Operating (Normal) Procedures for the Go-Around. By varying the Go-Around SOP an operator is NOT rendering invalid the certification basis for the aircraft.
It is not illegal to do what what Jetstar did. It is done by many other operators around the world frequently. The absence of process surrounding the change is another matter completely.
Mr Sandilands and others take note.