Pattern Recognition Gone Wrong in a Pawn Endgame

In this last game of an online tournament, I decided to aim for a superior endgame based on my healthy pawn structure vs. my opponent's broken pawn structure. Trading down brought me to the pawn endgame of my dreams. My opponent went along because he saw that he would have the only passed pawn on the board. But I reckoned correctly that my superior pawn  structure would allow me to blockade the pawn and put him in zugzwang, at which point he would have to abandon the pawn and be lost.

Everything went according to plan until my pattern recognition went off the rails at the very end. In time pressure, I saw a pattern that would lead me to a certain loss in a complex position, so I instead chose the clarity of a certain loss in a very clear position. I do not recommend this as a way to think about a chess game, of course! Given a choice between two bad continuations where one of them is much foggier than the other, of course you should choose the unclear continuation: The fog might be hiding a helpful resource!

Let's take a look at the game. Zugzwang and promotion with check will be important themes..