One of the links from the article actually provides a photo of a tear-down [1]. Apparently if you remove the label in the battery slot there is a hidden logo from Xiaomi.

[1] https://www.facua.org/es/images/noticia10806h_2.jpg

There are logos and the bootloader is chinese, people have actually inspected these phones.

That said I'm not sure what really the difference is these days...