I think it simply means you don't understand the difference between a fact and a prediction.
Like you, I also strongly think that TFB will start Week 5, but if you told me last APril that BB would spend a third round pick on a Michael.Bishop 2.0 QB who has a style and method of play totally the opposite of every Patriot QB since Bishop (with the exception of Kevin O'Connell), I would have even more strongly disagreed. I'm still confused about that pick. It defies seventeen years of BB drafts.
Mazz has it exactly right. These four games are an unprecedented opportunity. What if JG is really really good. He was drafted in the second round, starting QB territory, and he learned under Brady. What if JG is really REALLY good? Holy Crap.
With our star QB approaching the end of his run, we get to have a 4-regular-season-game at our promising backup QB. Forget Week 5 of 2016. Look at the possible effect his play and growth might have on the 2020-2035 seasons.
How can four regular season games not improve a backup QB? He will have experience and be better able to focus his training for the three remaining years the Pats realistically retain control over him.