I think the time is right to do the Vuelta after the Tour. He's had 3 years of riding a single GT, all podiums or wins, and last year there was the Olympics.
Now, with no Olympics or mountainious WC route, it's time to push the boundaries in GTs for Pogacar. Pressure on him to win will be lower if he wins the Tour regardless, and if he doesn't win he might salvage his season somewhat there.
Obviously he has to attack two GTs at some point but his other objectives (spring classics, UAE Tour, Lombardia) don't make it easy. But then again, it's Tadej f**king Pogacar.