Adding to this, not every company is obligated to show off crosslingual in demonstration. Seika, Ryo, Mo Chen, An Xiao, and Feng Yi did not. Karin did, but they mistakingly used her Japanese when trying to demonstrate Mandarin and didn’t replay it with Mandarin settings and continued on with the stream, so she ended up not having a proper Mandarin demonstration.
The entire point of crosslingual is to make these vocals an option for those languages. Dreamtonics, when introducing the function, said that it is supposed to make the voice fluent in all 3 languages. This benefits everyone who wanted the voice in a specific language but either don’t want to force tune it via phonemes (for tuners), as well as voice providers/companies who were not comfortable producing a voicebank in languages they were not familiar with.
I want to strongly point out that “fluent” does not mean “without accents”. That is something I really disliked when people were putting down “non-native language voicebanks” (Macne Nana English, Meiko English, Luo Tianyi Japanese, etc) and to be honest, when talking about people in real life (especially the latter is rude. People work very hard to learn as much as they can just to communicate in a language they are not native in). It was never promised that the vocals will sing “like a native”, just that they can sing in those languages fluidly and to make it possible for them to do it without having to record those specific languages. I don’t expect Kevin to have “accent-less” Chinese or Japanese. He sounds like an English vocal singing Japanese and Chinese in an American accent. Karin sounds and is a Japanese vocal singing in English and Chinese with a Japanese accent. And in OP’s case, An Xiao sounds like a Chinese vocal singing in English and Japanese with a Chinese accent. And unless they have more data in the other languages aside from default to improve the vocal even further (like Xingchen, and from what was announced, Weina), the accents /might/ be more prominent the less data it has. And to be honest, some people find accents very charming and just want the vocal to be able to sing it in the language they want, accent or not.
Honestly, considering how often I’ve seen comments asking for Utatane Piko English and Gackpoid English/Chinese all those years ago on Vocaloid Wiki and other places, this feature is basically an answer to this kind of request. It even happened for SOLARIA when one of the FAQ was about her getting a Japanese voice database and Eclipsed Sounds said that they couldn’t because Emma Rowley didn’t know the language well enough to produce a quality bank.
For Yuyao, it wouldn’t be unreasonable to expect a Taiwanese accent across all three languages.
Long story short, you buy a vocal built for a specific language and that’s what you get. They’re going to be accented in the other languages. They’re not always going to be “perfect”. If you’re not willing to work with the accent, the vocal probably isn’t for you unfortunately.
