In terms of the manual G87 acceleration vs the automatic, as
chris719 mentioned, a lot of the off the line difference may actually be due to 1st and 2nd gear torque reduction. With this in mind and looking at acceleration over 100km/h as being more important for track work, it looks as though the 6MT may actually have the same acceleration at higher speeds compared to the 8AT.
Autobild show an instrumented 100-250km/h for the 8AT of 19.5 seconds and 100-230km/h at 14.4 seconds (
https://www.autobild.de/artikel/neue...-22846107.html), Car and Driver have the 60-150mph (96.6-241.4km/h) for the 6MT at 17.6 seconds. The 96.6 to 100km/h difference is about 0.2 seconds and 241.4 to 250km/h about 2.2 seconds, giving 19.6 seconds 100-250km/h compared with the 19.5 seconds for the 8AT.
This reinforces 2 observations - the 6MT loses out mainly in the 0-100km/h range to the 8AT and the strong 3rd gear acceleration may indicate torque reduction to protect the 6MT in 1st and 2nd gear. Therefore I wouldn't expect to see any lap time advantage for the 8AT on a road track, only on a drag strip where the initial advantage off the line before 3rd gear is reached is maintained throughout the 1/4 mile.