Pulling a Nibali would be if Wellens went, or Soren Kragh, or Bilbao maybe.., with all the favorites looking at each other for a couple of minutes, and even then not going full gas, but some stop and go till the top of the Poggio. Sagan played a major part in Nibali's win, he didn't want to chase, and everybody else looked at him. Nibali by no means was a favorite on that day, he was an outsider, who tried his luck, had the strength, had the skill, and had the right circuimstances on his side. And it end as one of the gloriest days of his career. Deservedly so!
Now with Pogacar we had totally different situation, he was one of the main favorites, in superb form, and most importantly everyone and their mother knew that Pogacar will attack on Poggio. What Pogacar tried to do, is pulling a Merckx perhaps - aka riding everyone off his wheel, or trying to drag as few riders as possible with him, and try his luck in the sprint. But he didn't count on monster named Van Der Poel, or at least he didn't know monster is awake.