Since this movie is a movie about increasing class stratification and increasing class calcification where is it nearly impossible to move between classes unless you have something the very upper class wants (and even then you aren't ONE of them, you're working FOR them), it's interesting that Wilfred says that CEvans is the only one who's walked the whole train. That even Wilfred hasn't done so. It's interesting because initially I read it literally, and wondered why someone building such a massive train wouldn't have walked it to check on his creation. But then I realized as a metaphor it works. Wilfred didn't have to walk the whole train - at no point in his life would he have had to claw from lower to upper class. The society doesn't work like that. Those in upper are born there and will stay there.
Moreover, it also means that NO ONE from first class has ever fallen to the back of the train. What does that say about a society, that those with the most also have the most protections, while those with the least have the least?
And the fact that in the whole history of the train no one else has walked the whole thing, means that it is impossible to go from the very bottom to the very top. No one can do it. So it's even more important that CEvans, who represent the bootiest of bootstrappers to Wilfred, HAS walked the whole train. And his take away isn't, "Hey, I'm pretty cool. I can run this thing better!" His takeaway is (having seen the whole system and having metaphorically lifted himself up by the bootstraps) that the system is fundamentally broken. The system doesn't work, because he shouldn't have been the only one to travel the whole train.