I’ve noticed the same thing with ChatGPT. If I start speaking in Chinese first, and then ask it to say something in English it will speak with somewhat of a Chinese accent.
Yeah, the german is also hilariously bad if it's supposed to sound native.
From the two examples I could find on the page, it sounds stilted, but not "hilariously" bad.
Ah, yeah, the voice samples on the page are much better than the one in the video.