So let's assume that Eichorst had decided to keep Bo, and under pressure from the media and fans, does make a statement in November that Bo's job is safe. All is well, right?
Fast forward to next year. We're having the same kind of year, maybe a bit worse. And this time Eichorst really is undecided. Again, the media and fans ask for Bo's status. This time Eichorst declines to answer. You think speculation was bad when Eichorst says it's has policy to evaluate at the end of the season? How bad do you think it'd be when he's set the precedent to give a vote of confidence, but doesn't this time? And then what if Bo wins the Iowa game to save his job? Recruiting is still damaged by rampant speculation, and the hostility between pro-Bo and anti-Bo is even worse because the anti-Bo crowd was sure he was gone. And the speculation is just as bad the next year because everyone knows he's hanging by a thread.
There's a reason for having a long term policy and sticking to it.
Besides, maybe Eichorst really does evaluate the season as a whole at the end, instead of having knee jerk reactions to each win or loss.
The only person who deserved some feedback during the season is Bo. We don't know whether that happened. It doesn't sound like it from how Bo was talking, but Bo could probably be defensive in a 12-0 season. And maybe his job really was in jeopardy but Eichorst put out feelers for a replacement and wasn't getting takers.
One more thing, how many times have you heard an owner or AD give his coach a vote of confidence, and then fire him at the end of the season anyway? Even when Eichorst did it, there were still people trying to believe it only means Bo's job is safe until the bowl game. Even some of the media were trying to clarify the remarks.