Over on the Southwest web site, they are directing people to Westjet for connections to Canada. WN should warn their customers about the difference in policies on changes. Will Westjet accommodate a Southwest delay on a codeshare now or in the future? I try to use Southwest whenever I can. Westjet needs to consider being less AC and more WN.
Apples and oranges. The passengers in the OP were on a separate ticket with a different PNR. From the WJ standpoint, they missed the flight. Period. They didn't misconnect, because there's no connecting flight in the passenger record. As someone else mentioned, this is one of the risks you take when you don't have a through ticket from A to C via B.
Don't know how WestJet would handle it if the two separate tickets were on the same airline, but most airlines would say "tough luck" (and rightly so) and then do what they could to reaccommodate, but without any obligation.