I think that every GT should have a gravel or cobble stage tbh...
21 days are supposed to be a challenge and have all types of test for riders.
We have TTs, sprints, hills, mountains... cobbles and gravel have always been a part of road racing. They always will be.
The first ever tours had both cobbled and gravel parts to the route...
the first bike to win the tour is closer to a modern gravel bike than road bike.
If you cant deal with a bit of lose ground then you need to train it.
Landa would have won a Giro without ITTs...