The Translate TTS fails miserably, it sounds like its reading the translated text in english, with other latin alphabet languages. With chinese it just makes a single noise (probably trying to say the first character).
It seems to do this with every tested language.
Simply write some text from any language towards any non-english language, and press the "speaker" icon to have the app read it out loud.
I think it stems from the AI or whatever is running using english everywhere.
For the record I am on graphene OS, so maybe if you guys are using android libraries for TTS these might be missing?
Video:
It should speak in the destination language. Maybe voice packs should be an optional download?