Not necessarily true. If the application is already submitted they are far more lenient with this. When I first crossed the border to stay with my fiancé I was questioned about finances, ties to home, etc. much more so. Once I was married my application was submitted they stopped asking for any of that and renewed my visitor record numerous times without me needing to show proof that I would be leaving at any point in the near or distant future.
Agreed though, don't show up at the border with more than say your clothes, laptop, that sort of thing. They wouldn't be happy to see you there with a Uhaul. Hehe.