Another issue - crossing into Canada with temp registration?

Agree, I’d be AT the dealer raising he!! No reason for that kind of hold up unless they’re either doing something shady or just don’t give a f.
As far as the border, not saying it’s legit, but I’ve been across with valid paper tags (temp) on a new truck, trailers or campers with incorrect license plates or none at all on the TC (req in WA though) and with a car with no front license plate, several times.
Never a word about any of it. Mostly interested in asking me where I lived and whether I had firearms, 3x in a row!