Here we go.. definative answer from people who know (its sad ite not BMW.. they we're clueless!!)
The K50/K51 GS stanchions have been superceded four times, culminating in the current part number 8404842. This is because of issues with the aluminium top plugs not being crimped into the stanchions tightly enough.
All supercessions are interchangeable, i.e. all variants are the same length. So, yes, that is bull.
The ESA level sensors (6870000, identical front and rear) will indeed need to be recalibrated when fitting the replacement shocks. You can either do this at the dealer’s using their in-house diagnostic computer, or do it yourself by purchasing either the GS-911wifi or GS-911usb Generation 2 diagnostic tool. Here is a link to the manufacturer’s site;
https://www.hexcode.co.za/
The rear level sensor attaches near the upper left rear subframe mount, with a rod down to the rear swing arm, and the front one attaches to the front left of the main frame and has a rod down to the left hand side of the Telelever arm – obscured behind the left hand radiator. You shouldn’t need to touch the sensors, however.
Regards,
Stuart
www.motorworks.co.uk