Haha, they chose one of the most annoying fucking levels from CB to serve as the "challenge level". But it was a fun nostalgic trip to how rage- inducing Crash 1 was. Haven't finished campaign, but at least letting play the whole of World 1 would be pretty cool!
Boulders is only the 4th level of the first island, lol, i always thought Rolling Stones was a harder level, yes, there's a level on CB1 called Rolling Stones, lololol. Or Road to Nowhere, god, that level was infuriating.
Naughty Dog have always been a clever developer and it shows as far back as Crash 1. Boulders was indeed the hardest stage of world 1. Road to Nowhere would lead to too many broken controllers if it was used instead.