I had one as well, and when I was in Alberta too.
As for the exceptions, its bullshit, but TONS of things are exceptions. BMWs that have sport suspensions come with very little fender gap, but you can get a ticket if your "other" car is lowered to the same clearance.
Ford F-150s have stock side pipe exhausts(some years), but if you do one, you risk a ticket.
95% of older Harleys have straight pipes, and you all know that if you straight piped your car you wouldn't make it 2 min on a drive.
most modded 4x4 trucks have tires that stick WAY out past the wheel wells, but if you do that in a regualr car, you will get a ticket.
Muscle car guys can drive around with roll cages in thier car but we all risk getting a VI for having them.
etc.
The OP asked if they are legally a must. They are. He did not ask if they were really needed. And he asked, if he wanted to hear us say we hate the rule, well thats different.