I think the move Rowson's referring to is move 9. Since in the essay he says
"Yermolinsky offered a pawn as bait, and I very nearly didn’t take it because doing so would allow him to play a series of forcing moves"
So the only pawn that was offered and that Rowson took was on move 10 in reply.
The only reason I checked was to see how far a grandmaster was looking ahead, in this case 14 moves, which i find impressive.
"...I discovered a surprising detail right at the end of the line, in which my knight could retreat back to its original square, "
Like you, I wouldn't be impressed if he only saw from move 18 to move 24.
So the only pawn that was offered and that Rowson took was on move 10 in reply.
The only reason I checked was to see how far a grandmaster was looking ahead, in this case 14 moves, which i find impressive. "...I discovered a surprising detail right at the end of the line, in which my knight could retreat back to its original square, "
Like you, I wouldn't be impressed if he only saw from move 18 to move 24.