@Riot DMang - Vision Score of the Empire

Hey Dude! I read an older post of yours about the inner workings of Vision Score. There was a lot of great information and I learned that Champions like Ashe and Quinn can accumulate additional vision score by using their vision granting abilities. After some testing I found out that Swain does not have this perk. I was wondering if there was a specific reason for this. Is it because he only grants a small area of vision or it's low duration? Is it because it's not as easy for your system to differentiate between Swain using his W for damage or vision?