I understand what you're saying about expectations being too high within the fan base for Dak who has never even played a real NFL game (although I do think Seattle was pushing the bar for a preseason contest because it was the dress rehearsal, they hadn't looked good in the first two PS games, they were at home and Dallas had physically whipped them on their last trip to Seattle). I agree people are likely expecting too much.
However, I live smack in SEC country and watch a lot of it myself. The better SEC teams got to Dak early and often because of his surrounding cast and if that had "rattled" Prescott like you said... then he would have been that was for entire games at a time.
I saw it more as Dak trying to win a game that was pretty much unwinnable considering the discrepancy between the talent levels of he two teams. He was either being hit way too soon or he was taking what was essentially a calculated risk hoping that he could make something good happen for his team. I understand why you (and others) might see it as him getting rattled and making mistakes... but for Prescott, it was try to make a play or just take the sack... and not taking chances while getting sacked would never, ever win the game.
So he took risks that he likely wouldn't have with more competent team mates around him.
Dak is built so well that you could tell he wasn't afraid of getting hit. He never had the look of a QB getting beaten up with that wild Bradford look in his eyes. He wasn't worried about getting hit and the physical part of the game, IMO, didn't rattle him. He just wanted to win and with the only option to try to do so being throwing the ball down the field into coverage he probably knew wasn't favorable... he did so.
At least that is how I saw it while he was playing at State.
Now, does that mean he won't throw some bad passes now that he has a good offense around him? Of course not. Hell, he threw a couple of bad one's in the preseason already. He will make some ill advised throws, and he will get picked off some. That is going to happen.
However, he has made those bad throws at a minuscule rate when compared to other rookie QB's in their PS games going back decades. While we know he is going to make mistakes... he has shown that he does have poise, doesn't get rattled easily, can read defenses, make the correct throw, use his legs to get out of trouble, and that the big stage certainly doesn't phase him in the slightest.
You're certainly correct in cautioning people that Prescott is a rookie and is going to make mistakes... but I think the kid is also going to make some very good plays for the team and will hurt/scare defenses with his legs.
And the best thing about Dak is what I haven't even mentioned: His ability to inspire his team mates with confidence and the uncanny way that his team always, always plays for him like it is their last day on Earth. People run through walls for Dak and just like Staubach's team mates felt like he would win it for them... Prescott's teams always feel like he can take them to the promised land.
There is a chance Prescott is overwhelmed, I agree. There is also a chance he shocks the NFL too. I can't wait to see which it is.