It's worth saying that it's also too counterintuitive for Jonathan Cohn. He says right there in the text that he thinks a single-payer system would be better than the one Clinton proposed. The thing Clinton's plan was supposed to have going for it that single-payer didn't it that it was more politically realistic. But not realistic enough to say, be passed into law and avoid contributing to the 1994 debacle. So there are real limits to how right she was -- it doesn't make a ton of sense to say "politics aside, she had a good plan" when the plan itself was supposed to be a politically motivated compromise.
That said, Cohn raises the interesting point that while Clinton doesn't think she was wrong about Iraq, she does claim to think she was wrong about health care. But what does she think she was wrong about? Just about the political calculations, or were there some substantive problems? It seems like an obvious set of questions to ask.