Which Halo difficulty is canon

Sometimes when I look at the difficulties menu, I wonder which Halo difficulty is canon. As I look at other people's blog about the same topic, most blog told the reader that herioc difficulty is canon because in the halo 1-3 it said in the description of herioc difficulty: This is the way Halo was meant to play. However, I was skeptical about this so I researched I found a very old Halo book telling about the Flood. In this book it was mostly about the Level: Guilty Spark in Halo:Combat Evolved it said that once Master Chief exit his pelican he could found several shotgun which is true if you played that same area in Halo:Combat Evolved on Easy difficulty you can find several shotgun and ammo. However, if you played any difficulty higher than Easy the shotgun are not there which means that Easy difficulty is the most likely canon and its description from the Halo: Master Chief Collection supports this: “Your foes cower and fall before your unstoppable onslaught, yet final victory will leave you wanting more” .   This would make sense because Master Chief is potrayed as a unstoppable killing machine! This is the reason why I think Easy difficulty is canon.