At the interview stage all we've seen is an application form with 120-word answers, and maybe a demo. And we're interviewing 50-60 groups over 3 days. It's not that surprising that we don't know in great detail what each plans to do. But once we accept a group, we spend a lot of time talking about the product with them-- literally down to the shapes of buttons.

And this is true with groups that have already launched just as much as those that haven't. In any startup, most development happens after launch. Every (good) startup is sans ideas 6 months in, compared to what they'll eventually do.