I did an international arrival to USA departure transfer at YVR last month. Talk about a gauntlet. First there was somebody checking your BP and passport before letting you walk downstairs where somebody else checked your BP and passport. Then comes CATSA security which was s-l-o-w. Once that was complete then there was then a visual verification of your luggage on a TV screen (the CATSA screener used the info on the BP to bring up a digital photo of my suitcase and asked for verbal confirmation that it was mine). Finally off to USA immigration, which gets its own separate booth and officer for transit pax as opposed to the very long line of folks waiting to go through USA immigration in the regular lines. After USA immigration a CBP officer collects your customs declaration. At no time other than on the TV screen did I see my suitcase.