Not all shows and services appear available via voice search
Voice search returns shows that are carried on major services like Netflix, Hulu, or Amazon Prime. Asking for shows on channels like Crunchyroll or Funimation (both anime services) brings up no results. Sometimes a show on Funimation appears via Hulu since Hulu retransmits Funi shows. But shows exclusive to Crunchyroll are never returned by voice search.
It's not a bias against anime. Searching for the Netflix exclusive "Violet Evergarden" or the Amazon exclusive "Girls' Last Tour" works as advertised.