I believe MikeManx is referring to the line to hand in your slip after the baggage claim area, for customs, not at the immigration area right after the kiosks. The customs line can snake all the way past the baggage carousels if you are unlucky enough to come in after another flight, especially flights from Asia.

For the benefit of those not familiar with YVR the first stop, right after you use the kiosks, is immigration. The CBP officer just looks at your slip there, maybe makes a mark on it (I have Nexus so it is just a quick glance in my case and a chance for me to verbally declare food or anything else but the normal kiosks work the same way) and ask questions if they have any, then they send you through to the baggage hall still with your kiosk slip of paper. Once you collect your bags (or not as the case may be) then everyone exits at the same place; at the far end of the baggage area through a narrow Tensa-barriered lane with one, sometimes two CBP officers at the very end of the lane collecting those slips from everyone and looking at any marks made by the first officer. This is the bottleneck, snaking line that I think he was talking about. It can be really long. You hand over your slip and walk out the doors and it is here that they will direct you to secondary if they choose.