I should also note that it's not very surprising that AVL restructurings show up as expected O(1) empirically, since many AVL trees are BB-trees, and it's been

I should also note that it's not very surprising that AVL restructurings show up as expected O(1) empirically, since many AVL trees are BB-trees, and it's been shown for BB-trees under the assumption that the root approximates the median - which is certainly true in most experimental settings. So It's quite possible the expectation isn't O(1) for pathological distributions, not to mention sequences.