From a trip to Vancouver last week it seems no one ever looks at your ArriveCan directly.
If you scan your passport at customs, this lets the system scan your ArriveCan and the printout you hand to border patrol will tell them what they need to know (ie, not vaccinated, go to the testing line).
On disembarking the ship, I can only assume either they don't care about ArriveCan at that point, or RC provided the information via passport data and if you needed a test (in which only those who may have boarded with a vaccine exception would apply) they'd work that out prior to disembarkation.