Confusion About X2's Drivetrain

I've been casually looking at some BMW models recently, and everywhere I looked says that the X2 has either an on-demand AWD system that's usually 100% FWD, or a FWD biased AWD system that's mostly FWD.

But then on BMW's webpage for the X2 xDrive28i there's an "What is xDrive?" button, and the page that it opens claims that xDrive is a RWD biased AWD system.

So which is it? Is the X2 100% FWD until rear power is needed? Is it FWD biased? Or is it RWD biased?