I've spent a considerable amount of time operating in South East Asia, the Asia Pacific region, and in China, so I can speak from experience on this one.
In all of these areas, English is NOT the native language of the ATC personnel (Hong Kong being the exception) and AT THIS TIME, their knowledge of English is a “Working Knowledge” at best, so explaining an unusual onboard situation can be – at the least – challenging.
I realize that we are talking about Tiawan, but they are not that different from China (mainland), so be patient with me as I try to explain.
Imagine this. If you were in the Beijing tower watching the clearance delivery guy, and someone called Clearance delivery and requested “…airways to euphoria (any airport), you would most likely hear dead silence, accompanied by blank stare.
However, if the caller used the internationally correct term, you would instantly – and far too quickly I might add – get your ATC clearance.
Another example is, trying to explain to a mainland China (Taiyuan, Lanzhou, Sanya, Guilin control, etc) ATC controller that you have an intoxicated and unruly passenger on board, would not be easily understood.
Furthermore - culturally - they may not see the problem with that type of behaviour.
(...Fang Yueh-chiang (方粵強), director of incident investigation for the Aviation Safety Council, said the council would not investigate the incident... "His behavior did not lead to a plane crash, so there is no need for us to investigate...." ) pretty much proves the cultural issue.
However, the words “May Day” and “Hi-Jack” – being internationally recognised terms - would get you the immediate attention that you seek.
Is this actually a “Hi-jack” situation? No, not really.
But, would the use of the term "Hi-Jack" and/or "May Day", get you the desired response that you require?
(Read this carefully) In THIS region, Yes, it absolutely would, and may be the only way to get that response.
In fact, the Commander of this flight did the right thing, given the conditions that he was faced with.
Cheers /cj