We do know how Dak practiced and played with 3rd stringers.....heck Michael Irvin said he could be Aaron Rodgers or Russell Wilson after seeing the guy practice....Dak was 3rd string at the time. How soon people forget.
Maybe you did not know Dak was definite....but I did after the first drive in the preseason of Daks rookie season. Never did I think Rush or White would ever be a NFL starting QB. The mini camp reports of neither being able to command a huddle and Jason Garrett having to verbally address it in front of teammates and media is telling as well. Dak on the other hand never had trouble commanding the huddle. Everyone thought Dak was the real deal as soon as rookie mini camp.
First, you are still arguing something that is beside the point. The discussion was about not knowing where things sit with White right now, and you are making it out as if I am talking down about Dak.
And no, Dak was not 3rd string throughout the preseason as a rookie. Moore missed the entire preseason, so he started out as #2, and Romo was being handled with kid gloves because of his repeated injuries in 2015, so Romo only threw 6 passes that entire preseason, Dak was THE guy at QB that preseason, and Showers got the mop up work. In short, Dak got a much greater opportunity than would have been expected at the start of training camp.
Even so, that's not the point. Yes Dak played extremely well that pre-season. I've never said otherwise. And I was as excited about him as anyone. But people also have to be realistic and understand there are always guys that show up well in their first preseason, and then never amount to much beyond that, and others who don't stand out that end up having outstanding careers (like Romo). A rookie preseason hopefully gives a flavor of what a player might be, but it is not definitive enough to anoint or condemn. Time tells those things.
If you thought Dak would be great the first drive of Dak's 1st preseason game, more power to you, but that doesn't change the fact that 1 drive in 1 preseason game is not something that can be used as a consistently reliable basis for definitive decisions. There is no question that history has proved that over and over and over again.