That mostly refers to startups that haven't yet launched and don't know if their idea will get any customers, as far as I understand. historious already has quite a few paying users, so I believe I'm right to be stubborn in thinking people want this enough to pay for it (because they have).
This makes you a non player in valuation game. By having a revenue you cannot over project and hence cannot get a valuation to provide a worthy exit to ycombinator.
That's an interesting thought, but it'd be sad if they actually think that way. Actual success counts less than imagined one, because you can't inflate the numbers as much?