Typically you expect major Canadian hubs (Toronto, Vancouver) to have sterile transit, Hong Kong airlines being one of the airlines omitted from this "feature" is strange, they really should "warn" people of it

Yes, it's the traveler's responsibility to ensure Visa, a line or two warning on their website isn't going to break the bank, it doesn't even have to be nationalistic focused - just warn people it's not a sterile transit in Vancouver for HK. But then again once they do this they'll lose business to those airlines that does transit (Air Canada, Cathay) properly