But don't users of the app still have to line up at physical customs desks for an in-person interview? The most recent times we flew into YYZ and YVR from abroad, we had to queue up, make our declarations at the machines, then get a receipt, then line up again and present the receipt to an officer who asked us many of the same questions we'd already answered at the machines.

If the app enables passengers to bypass this second step, then great. Otherwise, at most it saves a minute or two. The main time-waster is the two sets of lines.