That video was published on Feb 14, 2015, which is when it is summer for the Southern Hemiplane. The sun is traveling around the South Pole at that time. Looking Westwards, not only is the sun left of the equator, the sun is also curving around the South Pole.
You're basing that on a bi-polar flat earth model. Fine. Let's check that.
Then during Perth's winter, when the sun is circling the North Pole, the sun should set in a right-ward or northerly angle. Does it?
And during Perth's summer, when the sun is circling the South Pole, the sun should set in a left-ward or southerly angle as seen from Hong Kong. Does it?
They should be the same.
You're a fan of analogies. Here's one. If the sun is following a racetrack pattern, then let's imagine one observer in the grandstand outside the oval and one on the inner track inside the oval.
As each follows the racers around the track, the grandstand viewer swivels left and right to watch. The inner track viewer has to rotate around to follow the race. Along the western bend, both viewers will be seeing the racers go right. The grandstand viewer won't be seeing the racers go left while the inner track viewer sees them go right.
Flip the track over onto the grandstand viewer so that he is now inside the oval and the other one is now in the grandstand. The situation is changed, but they both would agree on the bearing drift of the racers around that bend.
The challenge is to work out a way for them to watch the racers and see opposite drift. What would that track look like?