Ornn can walk through some Player Created Walls

Now I don't know whether this is intentional or not, but I main Yorick. Recently, when playing a ranked game, I had noticed that the Ornn was not using his E to clear my walls to get out, but rather, he was using his W while walking towards my walls. This allowed him to COMPLETELY walk past it. I know his W makes him unstoppable, but I sincerely doubt that this is an intentional thing, and had seemed like a bug. It was extremely frustrating, and I would like insight to whether this is intentional, or a bug.

Thank you Riot!