Of course, this is nitpicking :). For all practical purpose, this O(log n) is O(1).
If you are interested, I can try to recover the proof that the rotation step can be done in O(n), thus allowing to apply the master theorem on the main recursion and getting the O(n log n) result.
If you are interested, I can try to recover the proof that the rotation step can be done in O(n), thus allowing to apply the master theorem on the main recursion and getting the O(n log n) result.