I forgot to mention option #3.
Not enough brainpower!

I wasn't talking about options, but about general (psychological) attitudes.
I was considering not the "processor power," but its settings. Properly configured settings are sometimes much more important than power.

when I checked, I was able to complete the cheat passage in 6 days, and even then, after clearing the path a bit.

"I don't see how to get there in 5 days, so it's impossible. Why should I waste time studying impossible options? That's stupid."
This is exactly the kind of logic that is normal. This is the kind of "mental" setting that most people play with, including you.
And this is exactly what "Setting #1" is, as a result of which you boarded the train that is guaranteed not to pass through the "5 days" station.

But there are eccentrics whose settings are different. And they don't think "stronger," they just think differently.
"I don't see how to get through it in 5 days. So what? It's still possible, I just don't see it. So, we'll look, maybe I'll see it later?"
And so, all the "normal" people start developing a "realistic" 6-day plan, while one "abnormal" person engages in nonsense and starts collecting evidence that 5 days is indeed impossible.
And if iceTiTaN suddenly also engaged in nonsense and spent 2 weeks studying the absurd problem of 5 days, it is quite possible that he would make several small discoveries for himself and on the 16th day suddenly realize:
"Holy crap! You can actually do it in 5 days!"