Largely forgotten thing about that 2017 Piancavallo stage was that the race was actually all over the place with 100k to go as the peloton split on a descent and Dumoulin was caught behind. There was a long chase between the groups and Dumoulin himself had to start working to catch them on a 2nd category climb with 90 k to go but was lucky the front group had run out of domestiques and Quintana, Nibali, Pinot and most other gc guys weren't daring to go on a 90 km break without any teammates.
Then Dumoulin dropped pretty much at the beginning of Piancavallo but Quintana and Nibali were so bad they got dropped by Pinot, Zakkarin and Pozzovivo while barely gaining a minute on Dumoulin.
Yeah, that stage was weird.