exactly. In fact, I was really surprised when I saw B9. It could have played at B11 which was a 15 point move. But it decided to play safe because B11 even though big in point, would give back strong safe in the center. (it also lost 2 point ish in end game which is typical of Master)
Incorrect. It lost points by focusing its play only on the probability of winning. It's moves were not "sub-optimal", its moves increased the likelihood that it would win by something.
That, to humans, may look like sub-optimal play, but in reality it's the same way it was playing the entire time. By giving up points, it increased the chances of winning (because the points it gave up would never actually add up to a loss, but removed possibilities that could result in a loss).
How did you know that?