In my experience they are very accurate and never need adjusting in regular use but I must confess I don’t obsess about accuracy so haven’t attempted to measure them scientifically.
Taken from wiki “.....won the Grand Prix de l’Aiguille d’Or in 2010 for the Double Tourbillon 30° Édition Historique in 5N red gold (ie this watch); and the International Chronometry Competition in 2011 for the Double Tourbillon 30 Technique (my other GF at present)”.
The latter in particular is a pretty serious award specifically on accuracy.