[SCOTT26]

The Extra rear glass after the rear door .

This has never been on a BMW four door because the BMW symbolic hofmeister kink is always integrated on the rear door opening.
It is more elegant , models like the Touring and the X line need them to break up the expanse of metal around the C-Pillars.

BMW designers are against that as are engineers about lack of B-Pillars which compromises structural rigidity. As was found on the E31 BMW 8er Coupe.
So much so that had the late eighties early nineties recession not kicked in , that Wolfgang Reitzle the characteristic R&D boss wanted to re-engineer a B-pillar into the car.
A feat he achieved with the BMW M8 which included a B-Pillar that helped to bring about a substantial transformation of the car. But the crisis at the time killed the M8 and the BMW 850i Cabrio, but it did bring a more cost-effective 840i for those that "struggled" to reach for the 850i.

For those that pine for a modern 8er...


It is called the 6er now.