Americans and Canadians at Vuelta a España 2023
Based on the text, the season where a rider doubled up on winning both the Tour and the Vuelta was 2023. The text specifically mentions Sepp Kuss’s best grand tour stage result as his 2023 Vuelta win.
However, the article is dated 2025 and discusses the 2025 vuelta, so it’s referencing a past achievement. It doesn’t state who doubled up, only that Kuss had a good result relative to his 2023 vuelta win.