Yeah I'm pretty sure they debuted in Volo Guide, as they came along with other monster races like the orcs, kobolds, and goblins. But they e been updated and released with Ravnica, since Minotaurs are native to that realm, and Thereos because of it's Greek roots. 

I know Volo Races got overwritten since a lot of folks didn't like the races there. Orcs and kobolds had negative modifiers (-2 int and -2 str respectively), as well as poor skills (orcs are basically worse half-orcs and the only good thing about kobold was pack tactics).