Bill, we can indeed ask AlphaGo that as the position without the lower left approach-answer exchange is also in the teaching tool. It's 41% for black, so not quite as bad as with the exchange, but still pretty bad (-6% on the hanging connection version rather than -9%). So it contributes to the badness, but isn't most of it. I also wonder if part of the reason it likes the hanging connection version so much more is that it then views that approach exchange as good for black: if white then attacks the hanging connection group at k4 (a move given as balanced in the AG Lee review and the one An Youngil said was better in his review, but not in teaching tool) then there is a feeling f3 could become overconcentrated (if k4 already present and black approached I wonder if white would play a more territorially agressive move like b5 as black trying to punish that with invading the lower side is probably a bad idea with the hanging connection weak group too). I suspect worrying about playing too many stones on the lower side is a reason Lee went for the d10 instead of k4 pincer.
Edit: just to give a concrete example of how I could see f3 becoming overconcentrated. If black goes for quick life with hanging connection group (maybe not exactly now, but it's the idea) then 17-20 are locally cramped, but if you can live in sente and play a fast development it seems quite ok for black. Not sure about 21, maybe
a is more AG style, is
b greedy, or shimari top left?
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