A spin occurs when the airplane does not have yaw (sideways) control.
The same happened to an Airbus 320 that took off from New York.
The vertical tail breaks easily on Airbus airplanes.
I’d rather stick with Boeing.
I agree with you, but ...
There is a slightly different possible scenario:
PIC loses control of the aircraft. Aerodynamic forces and/or exceeding Vmax and/or attitude of the aircraft place excessive lateral force on the VS, and it shears off. The lightweight VS would then ‘flutter’ to the sea, leaving the much heavier aircraft to travel several miles to its destruction.
BUT to me the photo of the VS being fished from the sea was very telling — the VS was virtually intact in the photo, IIRC, indicating its attachment to the fuselage was the failure point.
Old photos of B-52s, for example, losing their VS to turbulence showed the VS itself had PARTIALLY sheared off.
I agree with you that the weak point in the Airbus design is the attachment of the composite parts.
I don’t speculate and will leave this to the rudder people. I only deal with facts... The initial BEA report does not support your conclusion...