It isn’t clear if you are speaking about the Canadian agents, or, if this started on the US side of the border. If it was the US agents, they were probably trying to keep you out of trouble. If it was the Canadian guys, I’d guess they were attempting a “gotcha”, with a strip search and dismantling the vehicle.
Best,
Ted
"...and the immigration interaction on the Canadian side began normally. After requiring the windows to be rolled down..."Yea, I missed that. Sorry. Wonder if the US guys just waved them through.
Customs guys all seem to have a Napoleonic complex, however.
Best,
Ted