Fly to Beijing, Cruise from Tianjin - do we qualify for 72 or 144 hours visa

Itinerary: SYD > PEK (40 hours) > Tianjin Port > Korea

Is my understanding correct?
- we DO NOT qualify for 72 hour free transit because this requires arrival and departure from same airport
- we DO qualify for 144 hour free transit because we can fly in to PEK Capital Airport and depart from Tianjin Cruise Port?

Many thanks,
Tina