Differential spoilers and crow brakes - different bahaviour on manual and FBWA/Stab modes

Hey. I’ve been using differential spoilers and crow brakes with my wing recently.
The thing I don’t understand:

  • in manual mode when I roll left, both left surfaces go up, and both right surfaces go down.
  • but in FBWA/stab modes, when I roll left, only the outside left surface goes up, the inner left surface stay at 0 position and both right surfaces goes down. Same when rolling right (but the inner right surface stays at 0).
    Why is that ? Is there any logical reason for this type of behavior ? If so, why is it different for manual mode ?