Dutch M..
Now to the HS: The intended "lift" for the A330 HS is downward. The speed vector of the AF447 HS on it's path down to earth, is also downward. The pressure gradient is actually pushing the air towards the airfoil. So no reason
at all for boundary separation. More the contrary: Because the downward speed vector "pushes" the airflow on the airfoil, the tendency to boundary separation will be less.
Another aspect relevant in this, is: The HS airfoil does have to curved surfaces,
bottom side a lot, the upper side just little bit. So both sides of the HS generate
lift, where the downward lift force is significantly higher.
Now back to the AF447 HS on it's downward trajectory. The downward speed
is so high that the upper side of the HS airfoil will have (nearly) complete boundary layer separation, so the upper airfoil surface is completely stalled. The net effect is an even greater downward lift vector on the HS.
That sounds very unlikely to me. You are suggesting that the HS is producing lift in the downward (negative) direction despite being at a severe POSITIVE angle of attack.
Imagine your explanation applied to a wing.. You're suggesting that a wing flown at a severe negative angle of attack (so severe that the lower surface is stalled) can still produce positive lift. I'm aware most cambered sections have a zero lift angle of attack that is slightly negative but your suggestion goes way beyond that.