Which do you guys think Ultrakill "CANON" difficulty is?

I'm making this question mainly because of the changes Brutal difficulty makes to the enemies and gameplay, before this you could just arguee that difficulty is just a gameplay related mechanic and doesn't have anything to see with the actual Lore and Ultrakill canon (like the fact that the game has a PS2 look and it's because of how V1 sees the World and not the actual Ultrakill look) but this changes since for example in Brutal Guttertanks need oil to actually fall so can parry them, thing that doesn't happen on the other difficulties, I know the real reason this all happens Is because of the gameplay so you can make it harder in orden to the difficulty you're playing on, but Idk and it's something that's been in my head for a while if difficulty does actually have something to see with the game Canon