There was an unofficial app released for the iPhone that actually did call your phone from your Google Voice number. I had never heard of the app you're referring to for Android phones and it is an interesting development. This is exactly why I wanted to sit down and collect as much accurate information in one place, so I'm glad you stopped by. For those of us who use the official dialer apps, they work as described in my document.
I would like to formalize the documentation of the app you're describing. Would you be interested in contributing to the doc?