Swain Vision of the Empire bug?

I believe there to be a bug on Swains Vision of the Empire. I do not know if it is a bug as I could not find any text explaining this behaviour as intended.

In a game last night I moused over to Baron pit to ping because I suspected the enemy team was going for baron. What I saw when I panned my camera over was the Enemy Swains eye from his W pop up in the fog of war in baron pit where my team had no vision.

It seems unlikely that its supposed to show the enemy where he's placing his eye in the fog of war, as it creates a tactical advantage for the enemy team for someone just using thier abilities normally. I don't have screen shots, and I'm at work, but I'm sure it's easily tested.

Edit: To clarify, the fog a war was still present where he used his ability, it did not provide my team vision. I could just see his eye and it's animations inside the fog, revealing where he used his ability, and strongly hinting that they were taking baron (which they were).