Originally Posted by Dave Noble

AA would charge the $150 fee if origin or destnation changes and in that case it is still just an award flight being held and changed. The passenger is still taking a flight albeit $150 poorer

Swings and roundabouts; some schemes are better for some things but not for others

In this case for a fairly small fee of $55 you can make the desired change ; if you had been using , say, US Miles, you would have been charged $150 ( if before departure of 1st flight in trip ) or just told sorry it cannot be done at all otherwise