Yamashita spent 40 minutes on the White 20 he actually played.
White 1 was believed to be the alternative he was looking at. Yamashiro Hiroshi suggested the variation shown as a likely outcome, but speculated that this was too placid for Yamashita. It would certainly not have been consistent with his aggressive new move.
The shape in question is not new, but previously - in the fewer than a dozen games that have it - there have been interfering stones close by. The shape, however, occurred again soon after when O Meien tried it successfully against O Rissei on 1 April 2004 in the Honinbo League, though again a large wall on the other side impinged on it.
The full Kisei game is available here.