CX888/889 on the YVR-JFK-YVR is usually very light loaded according to my brother's TA office. It is the HKG-YVR-HKG sectors that are usually full to the brim. Often when he checks there are no seats remaining on HKG-YVR vv, the availability on the YVR-JFK vv is still wide open.

Most people who boarded/landed in HKG for 888/889 either terminated/began/made connections in YVR. Goes to show the vast majority from NYC prefer the nonstop.