I doubt that the FA "made up" anything. On the contrary, the FA was most likely told that the pax would be rebooked and their flights protected. The FA relayed the information. Following departure, the pax implicated either did not have their flights rebooked, or there were further changes, none of which was correctly conveyed to onboard pax. There is no incentive nor motive for a FA to provide inaccurate information. Yes it might occur with a misfit, but for the most part, the FAs are normal people doing a job with the tools and support provided.
The responsibility for this incident rests with the operations group responsible for rebooking pax and providing general service during flight disruptions. They continually screw up. Whether it is due to under staffing or a lack of resources, it is obvious that the management of pax needs under these types of circumstances is not a priority for Air Canada. How many times have we seen similar stories, or for those of us who are not SE experienced this? AC consistently provides a negative experience when there is a problem. (And before the SEs chime in with the but I am greeted and escorted and blah blah blah, please keep in mind that us mere mortals who pay business class fares and who are not SE are often treated like crap without access to the concierges advertised, and it is worse for the unwashed peons in the back of the bus.)
The passenger was not treated appropriately and should indeed convey those sentiments to the airline. people do not pay business class fares to be treated like this.