It really isn't, though. The way these work is exploiting the fact that the backplate on the gun can be modified such that the out of battery safety (inside the gun) functions as an auto trip.
Which, coincidentally, is why US (and to a point, Canadian) regulatory agencies do their best to consider guns with safeties like this machine guns. They shouldn't; horse has already left the barn with that one especially considering full automatic fire is de facto legal and (even when in cases when it isn't legal) is trivial to achieve with guns that aren't Glocks, and this is something gun laws in the entire rest of the world have tacitly acknowledged for decades.
>People are buying
Not anymore, they aren't; the purchase, sale, or transfer of handguns is banned in Canada. Not that that's stopping the gangs, but those bans have never been about stopping crime anyway.
>I don't know why they're going out of their way to not inform people of what exactly is happening.
Who the criminals are, and the route the guns take to even get there in the first place, is extremely politically inconvenient for the Canadian government as it relates to blatant policy missteps that now affect Toronto, Ottawa, and Montreal.