If it is marketed as a pistol by manufacturer, then RCMP will in most cases consider it designed and intended to be a handgun (ie aimed and fired with one hand). Also, can anyone actually use the stock on a mare's leg? It's like 4"
That still doesn't make sense though. Again, the Henry Mares Leg have 12+" barrels, and are pistols stateside but rifles here. If the RCMP was basing their classification based on how they're marketed by the manufacturer then they would all be handguns in Canada which clearly isn't the case.
And No, you pretty much can't use the stock, that's the whole point. With a real stock it would be a SBR in the states due to barrel length, and practically nobody would buy them at that point.