Blatten is a natural negative split climb and they did the climb at a negative split, which is gonna bring down both the climbing time and the gaps at the end.
And I'm not really saying the model would be improved by increasing the discount because the number is too high, because there's many unknowns and you're never gonna adjust perfectly every time.
I tend to think we underestimate the W/kg riders can do when completely fresh in perfect conditions (ie: Contador doing 458 watts for 20 minutes) and as a result we may overrate performances when conditions were better than anticipated or riders were fresher than expected.
There was also a scientific study at one point where they had training data of TdF podium riders - one of which was Nibali in his TdF winning year by process of elimination and the 20 minute numbers he had were way higher than anything he did in races.
The pool of riders who can do good w/kg completely fresh is much greater than the pool of rider who can do it in a normal race situation (which are basically the successfull riders).
I can see in my data that many riders who have never won anything (much) have their climbing PB in MTTs, while all of the top riders have their PB in road stages.
The fresh data from Contador (and Nibali) is actually a bit crazy and I would take it with a grain of salt. In my system, perfect conditions are (-15) = -0.375 w/kg adjustment, I doubt many current top riders could do a PB after my adjustment completely fresh.
Indurain in his hour record apparently pushed 509.5 Watts at 81 kg for 60 minutes. (Ganna beat that by like 3 kph with 50 Watts less, crazy how bad Indurain's CdA was)
These are 6.29 real w/kg. If he pushes the same on a climb, depending on the gradient, this would be ~6.6-6.7 eW/kg which is a raw Index of 109-113. But with an adjustment of (-14), it is still only an Index of
95-99 (Effort not at sea level, thus not maximum adjustment).
This is a very high number for Indurain, but not his PB.