But you still don't need any sort of confirmation, when ASO bought Unipublic back in 2008 the deal was publicly announced and since then the Vuelta was listed on the organized events list on ASO websites, it's not something secret that has to be debunked through some covered clues.
Look here, showed on the first row next to the Tour https://www.aso.fr/fr/nos-sports/cyclisme
I'm not saying that I need confirmation! I'm just saying that it... shows it...