TBH I never really bother, as long as the box is grounded properly the switch will also be grounded. Though I think the point of it is when the switch is not screwed into the box (ex: middle of construction) then it is still grounded.
That is good to know, probably why I never done it myself. Lot of the stuff I've learned was from just seeing how others did it when I took something apart.
This is only true because even canadian plastic boxes have a metal bonding strip for the mounting screws.
US boxes have no such provision., if the ground is not connected to the device, the device is not grounded. Unless you're using an all metal box.