I mean, he technically was told, it's just that odio was fronting at the time and not duskie himself. and instead of telling duskie that "hey you're the murderer" these two dumbasses thought odio larping secret evil alter would be a better plan instead
tho their plan has some merit-- if Duskie doesn't know he's the murderer, he can't accidentally fuck it up or give it away, at least not as easily...