Your troubles might stem from the fact that all pawns are hookable, loosely speaking.
I thus define strictly operational:
A pawn hook is a pawn in a position that allows the opponent to advance an own pawn, and open a file for its rooks by a capture.
Now consider D.M.'s two positions and the h hook exploited by storming with the g pawn. As soon as the hook "grabs", the opponent has three options:
- Be captured
The first two lead to the desired line opening. Thus, Black might first advance its own h-pawn to h4 so that White can't play h3-h4 (even if this is a pawn sacrifice here, which might be the lesser evil). Compare to the position with Ph2: Advancing to h3 is answered with g3 (uh-oh, g2 stinks, but again, maybe lesser evil), advancing to g3 without reserves leads to the opening of the g line but the rooks stare at a protected pawn, and even if it is annihilated by again playing Ph4, its comrade on g2 still protects the king. Or maybe it typically ends like this: 1...g3 2.fxg3 hxg3 3.h3 and a piece sacrifice on h3 is needed.
Moral: Both positions offer hooks for a pawn storm! Strictly speaking, h3 doesn't create a hook, it moves the hook to an easily exploited position! It's just that the unadulterated f2-g2-h2 position is far more stable against pawn storms.