I think there is a big difference between "a cool presentation of your business plan" for the outside world and an in depth and detailed plan and research for your own.

I agree that "If you can't explain it to a six year old, you don't understand it yourself."

But this doesn't mean that all you need to know is, what a six year old knows. I notice that we tend to believe that having profound knowledge of your business is unnecessary.

But we don't need to bore everybody with this information.