Youtube not being blocked entirely

I have discovered that Youtube is not being blocked in my son's login as I had expected.  Specifically, if you enter http://youtube.com or just youtube.com, it is blocked.  However, if you prefix it with "www" (i.e. http://www.youtube.com or https://www.youtube.com) then you can get in.  I can't believe that this is an oversight.  So, I'm hoping it's just broken on my system and not others.  See the attached images below showing this.  Did I discover a bug or is there something I'm missing?

Youtube Capture_0.PNG