A330 has a Horizontal Stabilizer.
It articulates, making it in essence also a variable incidence wing.
With aft fuel, the THS must work against its primary function, that of keeping the Nose UP.
If the THS AoA increases too much it will STALL
If it STALLS, the NOSE will drop like a stone, and the a/c will likely ROLL as well.
A pilot, seeing the NOSE DROP, and roll right. WILL INPUT NU AND ROLL LEFT.
IF Pilot overcontrols, the a/c will CLIMB, perhaps alarmingly, and said climb may become unrecoverable.
just a thought.