Rear section is static. The front section slides over it which may give the illusion that the rear has moved, though logically there's nowhere for it to move to.
The tilted part you mention is the front section of glass.
The rear is fixed. But when the front section is opened it lifts up and slides backwards OVER the rear section. When it comes to a standstill it's tilted upwards at a slight angle.
That's what you're seeing in the video clip.
ahh an illusion then the video filmed inside the car looking at the rear look clear that's why I thought ah ha !! would of been nifty though if it tilted but I'm happy my question is answered thanks all.