[p750mmx]

Of-course your E6 is upscaling to 4k, if not, an untouched 1080p signal would be filling a quoter of your TV screen and not the whole screen.

This make sense, but I'm only paranoia why it doesn't show 2160p when I press the info button on the remote of my tv.

Why don't you use the HDMI 2.0 port on the BeeBox, there is a reason for that? Maybe you did explain this before but I don't remember if so.

3D is broken on HDMI 2.0 port. Intel hasn't fixed this yet so that's why you need HDMI 1.4 port if you want full 3D.

But did you try it with all settings in 4k resolution, desktop and Kodi, and choose the Interlaced method?