Is Ash technically the Pokemon Champion of Alola like Steven?
Yes, Ash is now considered a Pokemon champion of Alola like Steven.
However, Ash already was a 'champion' before becoming the champion of Alola, the champion of Orange Islands.

However his victory on Orange Islands is often disregarded due to the unconventional 5 gym battles without Elite Four, a Champion, or a Conference.

As mentioned on the Pokemon fan Wiki the following is required to become a champion


  A Pokémon Champion is a trainer who has beaten a region's Gym Leaders (in Alola's case, all 7 trials and totem Pokemon), Elite Four, and the previous Champion.