Clever disguise is creating duplicate (2 of the same) cards far more often than it should do it they are both random spells. It simply is happening far too often to be coincidence
clever disguise adds two random cards, which can be the same cards. if you have statistics that undoubtedly shows that it isnt random then please share that statistics here
Could you show your calculation for normal duplicate frequency and experimental numbers? There is not much spells in Standard you know.