Landa mentioned tailwind made the climb extremely fast. I checked and it seems to be the case - 6 m/s from south east on Passo Rolle (19 km from Fedaia). These are very favourable conditions for this climb and they surely upped Hindley's VAM.May be a hot take, but the effect of the 3rd week on the top performances in a GT are vastly overrated. It's really normal that the biggest watt bombs drop around the end of the 2nd week or in the 3rd. It's the tiring riders that get dropped that really go down, but the ones still good still drop their best performances.
Fedaia gradient is perfect for a high climbing performance. They did low watts all day before, then they blasted the very bottom too. Every thing inch perfect for high W/kg from the best climber, while many of the others exploded because they held on too long.
The factor that's more crazy than "third week" is the fact that it's at 1700m average altitude, and I'm not super sure how to compare it to a ~30 minute 6.5W/kg climb at 1100m average altitude.