That is just cathay Pacific policy, and some Hong Kong government policy, I see cathay they don't have flights out of mainland China, you would just need to book a flight with air China to Hong Kong, and have a ticket from Hong Kong using Cathy Pacific to Vancouver,
The following passengers are exempted from entry restrictions:
- Passengers who depart from Mainland China, Taiwan or Macau Special Administrative Region and have not been to other countries/regions in the past 14 days
- Their itinerary is included in a single booking, and
- Transfer time to the next flight operated by Cathay Pacific or Cathay Dragon within 8 hours
could these not work?