I believe the schedule change has essentially freed up an extra 744 airframe to allow for the 4x additional American services. The aircraft have less ground time in both SYD and LAX. I understand the Joburg flight turns straight around and goes to LA now, for example.
At present 2x 744s are required to operate SYD-NRT due to both flights being night operations. I believe the service can be operated with one 744 if the schedule moves to a day flight up, and night flight back op as per the rest of the Asian services and as per JAL's flights.
The above accounts for two 744 airframes, one for increased services and another for retirement.
Someone else may be able to chime in with better gin...
