Not going to debate which is better for road racing but the example you gave about the 2016 R wasn't with a tuned DSG. That would have made a big difference. I wouldn't even consider road racing in a stock tune DSG.To Repeat:
When VW decided to go for the fwd record at Nürburgring they selected a GTI Clubsport S with a manual transmission. Nürburgring is a long technical track with lots of turns. The weight savings was a primary consideration but the ability of the driver to precisely control when to shift was a factor. True; you can manually shift the DSG but than you are back to shifting manually.
Likewise in the 2016 "Lightning Lap" edition of Car and Driver a criticism of the 2016 VW R was the suspicion it's DSG transmission may have hurt it in the corners and speculated it would have been faster with a manual.
The DSG is an exceptional transmission but it is no match for a manual if the superior driver is driving the manual...