Bahahaha. That's a fun one. You missed this , which makes the status for the corner point ko. So you see, it's a little more complicated - not unconditional. And there was a prompt about capturing a stone in the corner (context: in one move).
But yes, or the point below it are better ideas for the initiated having fun with these problems.
49 kyu set is all about "spot the atari and capture stone by playing on the last liberty". It just introduces the idea there are less liberties at the edge of the board. Only the next set introduces captures in more than one turn and they are in unbranched sequences.
The example would need at least another White stone to be more correct, but even then hard to exclude all possibilities for forcing moves against it. Either way Mr. Mori is not known to frequent SL.
B captures on move 15, and bad result