ZFT:
I confirm.
Not just the A320 family either.
This seems unreasonable. My guess would be because the FBW system tends to mete out flight dynamics differences between aircraft sub-types, although that leaves operation in Direct Law hanging.
Yesterday, a Check Airman stated his informed thoughts on the matter and the reasons given were: proprietary data concerns, regular flight control software updates rendering previous flight dynamics models obsolete, how Airbus prefers to train thoroughly for the base model, then focus on differences training, and finally and most importantly (to the airline), cost.
Any of this ring true for you, ZFT?