You're making a hypothetical based on "with perfect accuracy"... but the much simpler change here (www vs. no www) is not done "with perfect accuracy", as clearly outlined by a bunch of comments in this thread.
So you're saying we should show all users www., just because that one site in a billion that shows a different non-www. page, for that one user in a million that would even notice that difference? Chrome is a browser for the mainstream people. The feature you're asking for is for power users and extreme edge cases.
