Let me debunk the fatigue element that people here are talking about when mentioning Pog at the Vuelta.
If Pog decides to go to the Vuelta he would need to hit hard on 2-3 days and then control the race. His training efforts are harder than controlling a field with no Evenepoel, Vingegaard and an injured Roglic. The Vuelta ends on the 8th September and if he wins he won't need to do World's and Lombardia. He can go on a 3 month holiday. He will be completely fresh by Paris-Nice next year. He would have achieved the impossible and be the first in history. This would make him a legend.
Now the second choice: World's and Lombardia. He would probably start training gradually one or two weeks from now and in September he should be doing monster efforts to achieve a peak in form. He would need to keep that form until the 12th October - the date of Lombardia. So that gives him one month less of holiday compared to the Vuelta schedule. His season would be legendary but nothing compared to a Grand Tour Treble.
Sepp Kuss this year in the spring was performing on his usual level. I don't think it was Vuelta fatigue. You need to look at his previous seasons to see that. Him performing bad at the Dauphine was because he was sick.
The real reason they probably won't send Pog to the Vuelta is team politics. If Pog goes and doesn't give a chance to Almeida and Yates for their own glory there is a chance that next year they will soft pull for him and won't be as loyal. Mauro knows this, Pog knows this, Matxin knows this but they will play the Vuelta fatigue card to the viewers.