The gentleman is absolutely correct... these short barrel pump shotguns with pistol grips are leglal and classified as Non-Restricted. Remington has offered a commercial version of the 870 with 10" barrel and pistol grip for years. I understand that Dlask is now making a conversion for the 870 that creates an 8" barrel, pistol grip 870 and maintains the non-restricted classification... this information came directly from CFC at a seminar about 2 months ago.
The legislation quoted above specifies: (b) a firearm that is adapted from a rifle or shotgun, whether by sawing, cutting or any other alteration, and that, as so adapted,
(i) is less than 660 mm in length,
CFC and RCMP interpret the phrase "adapted from" as meaning that the individual cuts, saws, etc. the firearm himself, not that he installs or has a gunsmith install commercially available components. This legislation does NOT include modifications made by a proper gunsmith, nor does it affect models that were either "commercially" made or those resulting from installation of commercially available barrels, pistol grips, etc..
If you take a standard non-restricted 870 shotgun... if you then purchase a commercially manufactured 8" barrel and pistol grip... if you then install those 2 items on your 870 shotgun... you will have a short shotgun as shown above and you will have done nothing that would cause any legislation to trigger a change in legal classification of the firearm. That was how/why CFC decided these were non-restricted.
If, however, you take your 870, cut the stock and/or cut the barrel then you will have created a Prohibited Firearm.
Don't know if this helps to understand the situation but that is how CFC explained it to us.
Mark