Hi
I posted on G7 forum about it a long time ago and also watched the borg warner video, I thought at the time it was odd that VW seemed to imply a fill for life system but couldn't find any further info when i asked the dealer, especially when its a clutch pack diff, or torque vectoring process. My rear BMW diff was fill for life but i manually changed it a 3 years with a extraction pump and refill. Porsche clutch pack LSD on GT3 requires a strip and rebuild every few years, so fill for life is unusual.
The dealer definition of "fill for life" is normally filled until out of normal service warranty and then "not our problem". But as you have found info I would happily pay £100 for a refresh at 3 years, but if its 1 ltr or less of Castrol high spec diff oil LS***** I will do it myself, same as the BMW.