In fact why is that word even two syllables? From what I understand, if two vowels are together (in English), it counts as one syllable only.
There can be confusions though - the standard way of writing pinyin groups whole words rather than individual characters, so something like "xian" may represent either "西安" (two syllables) or "先" (one syllable).
When I listen to recordings and to people speaking it, it sounds like two, which the Zhuyin seems to support.
Or... maybe he's thinking of Chinese opera. Yeah sure when listening to Chinese opera, all kinds of sounds get lengthened into many syllables ;-).
But really I can imagine how this happened. Couple of IPA wonks sit down with a Chinese native speaker, maybe a linguist, and they say, wtf, explain to us what is the difference between 'jun' and 'zhun'? The Chinese person does a hyper-exaggerated slow demonstration of the sounds, and they write that down as the official IPA transliteration that the OP is fixated on, further cementing a misunderstanding of real usage that was implied by the zhuyin transliteration.
As to Xi'an, pinyin has a rule for that kind of case, which is to add an apostrophe in between the parts to resolve the ambiguity.
https://en.wikipedia.org/wiki/Bopomofo
edit as reply:
>That's another rule. But in return you get 26 alphabets which majority of people on planet recognizes, instead of zhuyin which is only used in Taiwan and some Taiwan-related schools overseas.
I would argue the opposite; you don't actually get double bonus understanding of reusing language A's writing system on language B's, you get double misunderstanding. Aspects of each overlap on each other and the user confuses one for the other when they are in fact different and can't be dropped in as accurate substitutes for the other.
When they are dropped in as substitutes, unintelligible pronunciations are made. In the case of dropping a Latin writing system into a Sino-Tibetan writing system, this occurs even more frequently than when Indo-European languages are dropped in for each other.
If you want the right tool for the job, two different systems might be more appropriate.
>zhuyin which is only used in Taiwan and some Taiwan-related schools overseas.
I'm a rare example, but I didn't learn Zhuyin in Taiwan, nor did I learn Chinese in school. I reviewed the phonetic representations available and decided to use it because it happened to be the best supported by Pleco. If Pleco had IPA support, I would use that instead, because it's an even better tool for the job.
zhun, tun, gun, lun...
That's another rule. But in return you get 26 alphabets which majority of people on planet recognizes, instead of zhuyin which is only used in Taiwan and some Taiwan-related schools overseas.
That's a shock to me. Billions of Chinese people and millions of people learning Chinese are doing just fine. If anything, pinyin makes the first few lessons easier.
Of course I am not suggesting that pinyin can be used to replace characters, but it is good for learning pronunciations and useful in typing.
Japanese is different in the sense that each character already carries its own pronunciation, so the use of romaji is discouraged. But for Chinese, the character rarely reveal its pronunciation so you need a good way of describing them.
As for Pleco, ironically I see pinyin being featured more prominently, as the only pronunciation in the list view: https://www.pleco.com/
I may be wrong but isn't that only the case with hiragana and katakana? Kanji in Japanese can have multiple readings with multiple pronunciations - which you just kind of have to know.