I haven't played the game, but I'm going to assume that EmP picked the puzzle he revealed wisely. He's a good enough reviewer that such an assumption seems safe.
The problem with reviewing games that are heavy on puzzles is fairly straight-forward: if you don't give a good example from the game, then you can't really talk about the puzzle element convincingly. And if you can't talk about it convincingly, then why would you review a game that relies heavily on puzzles?
So yeah, I would say he had no choice but to reveal a puzzle. People who don't want spoilers sometimes scream that spoiling a puzzle in such a game is the same as a plot spoiler, but then they keep reading reviews anyway. While I don't advocate going around spoiling all sorts of puzzles and ignoring their complaints entirely, I do think that some people just need to get over the "every detail about a game is a spoiler" mentality. That or they just need to stop reading reviews.
"Too often we enjoy the comfort of opinion without the discomfort of thought." - John F. Kennedy on reality
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world