Not just trapped enemy king, but also protects own d-pawn(which is attacked twice and locks down enemy knight.)
Though honestly, am bit confused where the persistent advantage comes from or goes to.
At
material advantage is two black pawns for white's knight, position looks tactical, and local stockfish gives +4,6.
While it waxes and wanes for white's 8th to 25th move, SF-claimed white advantage is persistent for the position, suggestive of forced trade of IQP for rook at the 25... Ra8 variation.
Expect, when black gets off g5 and white moves f4 bishop to g3, white pretty much loses the advantage, whether on 25th or 24th black's move. White can force an exchange of knights with Be5, so what's with that?
I can see it preventing Be3+ in one variation, but that's about it.
(The suggested 20.g3 further emphasizes the IQP and queen-rook battery, I guess.)