I believe that Customs only randomly opens packages unless something draws their attention.
I would also think that a smaller package containing a smaller knife may get their attention quicker.
Most prohibited knives in Canada are smaller such as switchblades and balisongs, so Customs might be more inclined to open smaller packages
They may also been simply acting as tax collectors and saw the name of a business on the package and figured they needed to collect the GST


The stripes of a tiger don't wash away. Be a man of steel not clay JYD #102