There have been a few times in history where the strongest on the Mur goes too soon. Sometimes, like Gilbert in his unstoppable season, it doesn't matter when you go, because you're just that much stronger than anybody else. Others just know their own threshold and timing - Anna van der Breggen always had her own marker for where she would go, regardless of what others were doing, because she knew that was her optimal strategy for how long she could hold attack pace on the Mur.
Demi seemed to have it with dominance but she went too soon and almost threw it away - but she was strong enough for it not to matter in the end. Pieterse is so good on this hill though, she will surely win here one day eventually.