Destination AA is only used after you have reached cruise ALT or activated the APP phase.
Cruise ALT? Can anyone confirm that FMGC can NOT go into GA phase from phases other than APPROACH PHASE? (A320 FCOM DSC-22_20-30-20)?
My understanding also is that SRS GA mode can still trigger regardless of the FMGC phase provided Conf 1 or more selected.