Snowpiercer - Why do reviews seem to treat Wilford's casting like a spoiler?

Just saw Snowpiercer, pretty enjoyable if very weird. I was just wondering why seemingly several reviews I've read take great pains not to reveal that Ed Harris is the person who plays Wilford. For example, Peter Sobczynski's review on Roger Ebert's site contains this warning: "(Again, if you have any sense of surprise, do not look up the identity of the person playing Wilford.)"

I'm just wondering why reviewers were so cagey with mentioning this fact about the movie. Does it have something do with Ed Harris specifically? I thought maybe it was because Wilford functions a tiny bit like Harris' character in The Truman Show? But I know that's a huge stretch. Am I missing something here?