Whatever the merits of linked vs unlinked SS are, IMHO the facts do not suggest that the outcome of AF447 would have been different with linked SS,
Up to the point where the airplane stalled, the PNF was aware of what the airplane was doing and that the PF was doing it. If he had felt a need to feel the movements of the SS, feeling those erratic movements would not have added anything to his understanding.
After the airplane stalled, the PNF's understanding of that fact was no better than the PF's and his response to the excessive rate of descent was no different from the PF:
02:11:21 But we've got the engines what's happening?
02:12:13 We're pulling
02:13:40 Climb, climb, climb, climb.