This is demonstrably false, since just last year he rode both the Tour and the Vuelta and could easily have won both. Vingegaard is not a fragile rider, rather the opposite: his strength is his consistency and his stamina. He looks fragile, that much is true.
For Pogi I think the Giro was clearly an extended training camp for the Tour, and it obviously worked. Something similar could happen for Vingegaard. But Giro or no Giro, I think we'll see a better Vingegaard in the Tour next year, purely because he'll have a way better base as a result from not being in the hospital two months prior to the race.