The OP talked about
Hand flying an A330 at altitude in Normal or Alternate Law in benign conditions demands a high degree of skill and concentration, considerably more so in Direct Law. In moderate or greater turbulence it becomes progressively more difficult. required to hand fly the aircraft at high altitude..........
It would be easy to confuse "difficulty" to handle the aircraft accurately at high altitude and............ stability, and a whole host of other issues.......
Fundamentally,
All aircraft are more difficult to fly at high altitude because of some pretty basic physics. Even those with a high degree of positive stability.
Think, Effects of Controls. High TAS, low IAS at altitude and momentum.
All this happens irrespective of CG, dynamic stability, computers, FBW etc etc...
Throw the above into the mix and it all gets incredibly complicated..........