I think you need to distinguish looking good throwing the ball and ready to run the offense. In fact, even given the reports of Bridgford at this point, I would suspect he's not ready to run the offense today. I think he will be by Fall - between now and then he is going to get a lot of work. But remember that, because of the injury Bridgford really had very little healthy practice time before last fall. My guess is that if we had thrown Bridgford in, he would not have looked good, maybe even would have looked terrible, though his throwing probably would have been good.
That being said, I would have thrown him out there and see what he could do. If, instead of Mansion, we had Robertson, or Levy, or even Ayoob, I would not. But it was clear that the offense was going to go nowhere. IMO, Tedford is too protective of the psyche of his young QB's. I don't know if that is his nature or if he had an overreaction to Ayoob (which would not be his only overreaction to Ayoob). On the flip side of that, he may have really been not ready. Also, we were doomed when Riley went down. I knew going into the season that we would be doomed if Riley went down. Really, what we are talking about is whether we beat UW, because we were probably not going to change any other outcomes with Bridgford. At least by UW, though, I would have said "why not?". Give the kid some experience and maybe give the team something postive to go into the offseason with. I would have told him that he could only improve his stock, not hurt it, and that he should go out and have fun with it.
That being said, it may or may not have been the wrong decision, but it was a common decision and, drunk, if you are thinking it says anything about Bridgford, I'd point you to Andrew Luck. I'm sure Luck looked good in practice behind Pritchard. And its hard to believe Luck would not have been better than Pritchard from the get go.