Attack v Defence

ASSESS this middlegame.

White has just played 15.Qd1-g4 in Tarrasch - Janowski, Ostend 1907

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"Although the black king's defences appear to be adequate, the frontal attack, initiated by (15.Qg4), wins all along the line," writes Tartakower in 500 Master Games Of Chess. "What follows is a masterpiece of clarity and conciseness in chess."
Nevertheless, the engines Stockfish10 and Komodo9 reckon the position is dead equal.
15...Qe8?
"Or 15...Kf7 16.fxe5 dxe5 17.Rf3, and the black king's position remains precarious. After the text move, White's f pawn becomes a battering-ram."
The engines reckon the line given by Tartakower favours Black, if anyone, with Stockfish10 being particularly gung-ho at first after 17...Be7. Eventually both engines come to give Black a slight edge after 17...Be7, with Stockfish10 equally liking 17...Rh8. I presume their assessments are based on Black's king being safe behind its wall of pawns, especially now White has no kingside pawn breaks (h4-h5 is not feasible). Meanwhile, Black has the half-open h file to work down, and the better minor piece. After the text, White is able to use the pin on the g file to further his attack.
It should be noted that on general principles, 17...Kf7 was the more natural move in that a) it breaks a pin, and b) kings are usually safer when in touch with their defensive pawn-wall.
I think it also illustrates what is fairly well-known, ie that attack is easier than defence. One mistake by a defender can be fatal, while a mistake by the attacker often only leads to equality or at worse a slightly inferior position.
16.f5 exf5 17.exf5 Bxc3?
The bishop was hanging, and at first glance it seems a good idea to give it up for a knight that could help White's attack. But the engines much prefer 17...Bc5+ 18.Kh1 d5, denying the knight the e4 square while keeping the bishop for defence. However, they still like White's position, and it does look easier to play.
18.bxc3 Kg7 19.Rf3 Rh8
"If 19...g5, 20.h4, which the move in the text is to prevent."
20.fxg6 Qe7
"As 20...Qxg6 is not feasible, on account of 21.Qd7+, Black's position, with a powerful wedge driven into his game, gradually becomes hopeless."
21.h4 d5 22.Raf1 Raf8 23.h5 Rh6 24.R1f2 Rhh8 25.Qf5
"Vacating the g file for the triumphant entrance of the "third Musketeer."
25...Qd6 26.g4 Qe7
"Hoping to control the critical square g5."
27.g5!
"A decisive advance."
27...fxg5 28.Qxf8+ Rxf8 29.Rxf8 Qxf8
"There is nothing left. If 29...Qc5, 30.d4 exd4 31.R2f7+ Kh6 32.Rh7(or Rh8)#"
30.h6+
According to ChessBase's 2019 Mega database, the game ended here, but 500 Games continues:
30...Kxh6 31.Rxf8 Kxg6 32.Kg2 e4 33.dxe4 dxe4 34.Kg3 1-0