It's all in the delivery though, right? You can make a passionate case for your current traction by stating metrics with conviction. You can also recite them in a very rehearsed-sounding way.
I think the point here is to show that you know your stuff. instead of saying "we're growing rapidly" or "approx doubling users every two weeks", have numbers to demonstrate your command of the situation.
Basically, "I need to answer X, and phrase Y is a good way of saying it", rather than "Better memorize this 5 sentence script answering that question".
In situations outside of interviews like this, I've stumbled over things I should have known simply because I had the butterflies. I wonder if I had rehearsed, maybe it would have solved that slight hesitation you alluded to?
When you memorize data points, you actually become more familiar with it, and you can say it with more confidence, more naturally. You've said it so many times it's like walking.
I just object to the whole 'study study study' BS that is now normative for interviewing, because it's encouraging 'gaming the system'.
YC had their biggest hits with the 'loose' style, maybe they should go back to that.
I'm lucky to have largely avoided it, but having to create and do pitches all the time is utterly annoying. If it were for customers yes , then essential. But for others ...
One approach would be to give no advice at all, to be totally quiet about intent and motivations, so you catch people in their natural states.
Finally, I would hope they are collecting data on all of this.
I'd love to see the A+B test on 'interviewed but passed and interviewed but rejected'.