I'd like to point out, that we have no confirmation of Roglič peaking too early for the last years Giro, but we do have a story from Roglič himself, that he's had serious digestion problems and didn't feel well or as we might say, he was and felt ill. (Now one could argue, that his illness is the result in (in sense of materialisation) of his early peak, but a lot of people get ill without being pro cyclist that peaks to early). Then came the team cars "natural break" and subsequent accident, which was much worse than he was ready to admit at the time, trying to still scrape something out of the Giro, even though abandoning was seriously contemplated. Now I might be naive, but I believe that Primož does not like to talk often or much, but when he says something, he is above all else, honest, so I believe the story.
What can also be said in retrospective is that Nibali was very right when he said "Roglič is not gonna win the Giro ridding like that" after Roglič preferred to mark Nibali at all cost and let Carapaz get away... Of course Roglič (or Nibali) at the time could not foresee the problems awaiting him around the corner, and it can be a mildly interesting "what if", to speculate how the Giro would go if Roglič just tried to take all the time he could when he still could (if he (as I believe) actually could).