Here's a link to the game Rowson mentions against Yermolinsky. The critical position ("Yermolinsky offered a pawn as bait...") arises on move 18.
It's not spectacular - I would say mundane, but you can't say that when someone beats a top GM in just 24 moves. What Yermolinsky overlooked is a famously missable type of move - a backwards move to a square that was occupied at the start of the variation - but still trivial for a player of his class.
It looks to me like he did not like his position after move 16 and sought these complications partly as a bluff. The computer says Black's position is not all that bad after 16...dxe5 or 18...dxe5, but he will have to either defend a passive position with a weak d-pawn or sacrifice a pawn in a different way.
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.
The parent comment is correct -- "offering a pawn" means allowing the other player to capture a pawn without yourself having an immediate way to regain it, usually banking on some kind of other piece activity as compensation for the material.
On move 9 it is a simple exchange of pawns and since the material remains equal after the resulting sequence of exchanges we would not refer to that as offering a pawn.
It's not spectacular - I would say mundane, but you can't say that when someone beats a top GM in just 24 moves. What Yermolinsky overlooked is a famously missable type of move - a backwards move to a square that was occupied at the start of the variation - but still trivial for a player of his class.
It looks to me like he did not like his position after move 16 and sought these complications partly as a bluff. The computer says Black's position is not all that bad after 16...dxe5 or 18...dxe5, but he will have to either defend a passive position with a weak d-pawn or sacrifice a pawn in a different way.
https://lichess.org/oLuNYymZ/white