U.S. Immigration does have full rights to operate at YVR as if they were on U.S. soil. It is a strange set up, but that's what AIF pays for.

Also, when I was there last summer my traveling partner got the full-on secondary because of some of the mountaineering gear in his checked luggage. I mean, he got wanded, patted-down and all of his luggage *thoroughly* hand-search. However comma, they were as nice as can be. But it did take some time, as I waited for him after I'd gone through the metal detectors.

That said, about every 4th or 5th pax was gifted with a secondary, random wanding that morning.

I guess the moral of the story is, YMMV.