If they haven't been taken down already, there isn't a problem. There isn't really anything saying you can't use that difficulty in the category rules.

it says in the rules no difficulty under casual so yes there is a rule

I see the rule, but in the part about the specific category rules, it doesn't say anything about that. Though, I do realize that is an invalid point.

the rules are for the entire game not just one category every catagory 100% 1-2 it all the same rule so im still confused why that runers runs are still live

I know the rules are for the entire game. I personally don't think it's a problem, though. A mod did a run and it was in story mode, so I don't think we should be worrying about this. If you want to do it story mode or casual I think that should be up to you. The only difference iirc is that you have limited lives on casual, so it's there if you want a challenge ig.

Well it'll make a difference in full game runs tho

But while its deathless its fine