Was IRl Digital called a "hero" or "勇者" before? I recalled some JP race horses were called that but I don't remember who soecifically
Kinda yes. JRA ran a poster featuring Agnes Digital (See #54 of this page) with the catchphrase "A True Hero Does Not Choose His Battlefield" (真の勇者は、戦場を選ばない). So he's sometimes also called "Hero" (and IIRC JRA was pushing for that epithet), though his fan-preferred epithet is "Deviant" (HENTAI) or some variation on HENTAI.
Uma!Digital sometimes gets called Hero when the fanart emphasizes her serious side as opposed to her usual *BOHEE* fangirling self.
Other horses called "Hero" include Contrail (Hero of the Azure Sky, 青空の勇者). There's also Deep Impact (sire to Contrail), though that one is 英雄 (same "hero" used in the Fate series, as opposed to the DQ yuushas) instead of 勇者.
Yuusha Digital to Maou no Shiro
Digital the Hero and the Demon King's Castle.NEW PROGRAMME