There are some things that are really identical to MIUI user interface.. and you're right, it's strange.. like the notification bar or whole menu style, but the ones they changed and that are visible from the video aren't so impressive in my opinion..
flat icons and others similar things (nice but nothing different from the current global UI trends..) can be just a theme, camera app (probably a custom one) looks horrible, the task manager with screen preview is clearly better than the one that current MIUI v5 has but it's nothing more than what you can find on any other android stock or basic custom roms (but app lock in memory feature is like MIUI)..
Transitions and launcher animations seems also a bit laggish for being an octa-core device with 2GB of ram.
But I'm curious to know what they did, it's not MiHome launcher, so they should have ported/copied/(stolen?) MIUI rom (whole rom or some portions) to their device and changed some things or for some reasons they got V6 beta code..