He also said "thin" filters. Those of us that own the 16-35mm L might think twice before we use the ultra thin CPL's and filters we used on that lens on our 24-70mm II.
It wasn't cheap or thin, it was cheap and thin. I have no issues with the B+W XS-Pro thin mount filters on either my 24-70/2.8L II or my 16-35/2.8L II.