It's clear from the Chinese version of the site that it's 4K: http://www.mi.com/mitv

That's a different display. Look on the tech specs page for the chinese one: http://www.mi.com/mitv#params and compare it to the OP: http://www.mi.com/en/mitv#fullspecs

For example, the CPUs are different, one's a snapdragon 1.7GHz, the other is a Cortex A9, 1.4GHz. (Different GPUs too.)

Not to mention one explicitly says it's 1920x1080, while the other is "4K".

The tv on chinese page is MiTV 2, which is the second-generation MiTV, while the one on en page is MiTV, which is launched several months before. It seems that MiTV 2 in en page has not updated yet.

You're right. There's a number "2" after the name of the TV in Chinese. Maybe the Chinese site is the second generation Mi TV.

The price on the Chinese page is 3999 yuan, which translates into $641, indicating this is the model the OP meant. So it looks like the OP linked to the wrong page by mistake and got version 1 instead of version 2.