As per Air Canada's website, flights connecting in Vancouver that arrive from Japan do not require baggage collection (assuming all flight sequences are through Air Canada). The link even has a map telling you where to go:
https://www.aircanada.com/us/en/aco/...rt/int-ca.html
So it seems like he shouldn't need to collect his bags, and he should check them in Osaka and receive them in Montreal. He can also double check whenever he's checking in at Osaka and ask the staff to confirm that he won't need to collect his bags in Vancouver.