Guess The Move

GOING through an old copy of Chess (September 2017) this morning, I came across a move I am pretty certain would never have occurred to me.

Black to make his 20th move in Jovanka Houska (2402) - Gawain Jones (2660), 2017 British Championship round seven

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20...g5!?
Jones, who is pictured on the cover of the magazine as he went on to win the British title in a playoff against Luke McShane, explained his thinking thus: "My g6 pawn was just getting in the way of my knight's ideal journey to f4, so I decided to get rid of it."
Jones awards his move a single exclamation mark. My reaction on first seeing it was that the move either deserved !! or ?!
Analysis engines struggle to get the move, or at least at first. Show them the move on the board, give them enough time and, for a while, ...g5 comes to be Stockfish10's top choice and Komodo9's second choice. The latter engine is consistent in preferring 20...Kh8, but Stockfish10 flitters between 20...Kh8 and the text.
I am perhaps being curmudgeonly in annotating Jones' move with !?, although I am sure he would not care an iota either way. Whatever the punctuation, ...g5 is a brave, and to me, amazing move.
The game continued (notes in italics by Jones in Chess):
21.Qxg5
The engines suggest leaving the pawn where it is and instead bringing the a3 knight back into play with 21.Nc4.
21...Rf6
Now White has problems with both her king and queen.
22.Kh2?!
The engines come to strongly dislike this natural-looking move, preferring 22.Bh2, 22.Bh4 or 22.Qg4, although favouring Black in any case.
22...Rg6 23.Qh5
23.Qh6 Bh6 hardly helps. One illustrative line runs 24.f4 Kh8 25.Nc4 Rxg3! 26.Qxg3 Bxf4.
23...Rf8
Black's position plays itself. All I need to do is point all my pieces at White's king. In the meantime White has absolutely no counterplay and the extra f3 pawn just gets in the way.
24.Nc4 Rff6 25.Bh4
Bringing the knight over to the kingside with 25.Ne3 fails to 25...Rxg3! 26.Kxg3 Rh6 27.Qg4 Rg6.
25...Rh6
The computer points out I could also have played 25...Nxd5!? 26.exd5 (26.Bxf6 Rxg2+! 27.Kxg2 Nf4+ is the subtle point) Rf5.
26.Qg5 Ng6
Six moves later, the knight gets to use the square vacated by Black's positional pawn sac.
27.Bf2?!
This loses immediately. 27.Bg3 at least covers the f4 square, but after 27...Bc8 White will still be unable to defend against all the threats.
27...Nf4 28.Qg4 Qe8
White's queen is trapped …
29.Ne3 Rgf6 30.Nf5
… as if 30.Qf5 there's 30...Rh5.
30...Rxg4 31.Nxh6+ Bxh6 32.fxg4 Nd3
32...Nxg2 33.Kxg2 Bd2 was the alternative, but I thought it would allow White to put up further resistance.
33.Re2 Nxf2 (0-1, 38 moves)