There is a risk Vingegaard will fade or have a breakdown. But not automaticaly. Van Aert proved it a few years ago. After appendicitis and surgery, the recovery, starting to ride carefully and finally training during the second half of June, Van Aert went to the Tour without Dauphiné or Tour de Suisse. Performing moderate the first week, and then start riding astonishingly strong. Resulting in three stagewins and great helper work.But he also had more time to come back from that injury.
Look, I'm not trying to say that he will be at 100%. I just think that this nonsense about how he can enter the tour at whatever% and than get better by the third week is a bunch of crap. Not in todays cycling when they go full gas every day.
Bad preparation has a tendency to show late into the GT. I believe he will start and if he does his numbers will be good enough for him to think he can win it all. The real problem IMO will be sustaining that form for 3 long weeks with the kind of preparation he had.
So, everything is possible. Being destroyed by Pogacar, maybe even Roglic and others. But equally hurt the weakening Pogacar (because of his Girofatigue) during the last week.