I can see Alaphilippe try and hang on to Alberto when he attacks, and I think the fact that Alaphilippe rarely rides in a calculated manner, but instead responds instantly to attacks will present itself as an opportunity for Alberto to really try and crack him. He is not the worst opponent to ride against for Alberto in that sense - but 1½ minutes is a lot and will likely require that Alberto gains time on more than one occasion. Also, there are 5 other good GC riders (I don't count Gilbert) in front of him, that he also needs to distance.