OP made a valid point, and OP presented it well.
I'm surprised that anyone would reply that it's okay for Courtyard hotels in Canada to ignore Marriott's terms & conditions. Anywhere in the world, it's a simple matter of converting $10 USD to the equivalent amount in local currency. That includes Canada.
My only question now is about the topic name: "Canadian Courtyards give $10 CAD not USD in F&B credit as Platinum Welcome Amenity."
Can this really be said about Courtyards (plural) in Canada? Or was OP's experience with a substandard Platinum Arrival Gift an isolated incident at one particular property? If this were a widespread problem, I would think there would have been a lot more discussion about it here on FlyerTalk since August 18, 2018.