is a clever tesuji. After the local temperature drops to 3 1/3 points.
Later - is sente. If is at a, White later needs a protective move.
After the local temperature has dropped to 1. A play at b has a miai value of 1, a play at c has a miai value of 2/3.
has a miai value of 4 1/6.
(Note: While I am criticizing published solutions with incorrect values, getting them right is not always easy. This is my second version. In an earlier one I was off by 1/6 point.)