TMR put this up on their Facebook asking who has to give way, but that's too easy. A much more complicated question is: what does the law say around indicating?
I've seen people say only blue must indicate, others say both must indicate, and yet others say neither must indicate. Which is correct?
How would the bike indicate in this scenario? With a left indication while not changing direction or lane? I would interpret that as them wanting to leave the road on the left side after the merge and indicating it impatiently.
In the example videos, the vehicle in the bike's position did not indicate. It's not explicitly covered but it seems like the expectation is that only the vehicle in the left lane indicates (i.e. only the car, not the motorbike).
That's for Australia. In NZ it seems the expectation is that both vehicles indicate (this is how I do it, but I'm in NZ so that makes sense).
Neither country seems to explicitly say it's required in official information.