Originally Posted by
Bohemian1
I'm not sure that is true at YVR, but I have no recent data points other than
this press release.
From the link you posted:
The U.S. interviews are completed by U.S. CBP at Canadian airport preclearance locations for ticketed passengers departing Canada for the U.S. that same day.
Not sure of the exact logistics at YVR, but at YYZ immediately after preclearance you go through the sliding doors and then stop and wait before the accessibility help desk.