That's indeed much more natural and common —and symmetrical to X, Y, Z and geometrical, too, often used in triangles.
Established in dictionaries and many, many texts:
άλφα2 ο, someone unnamed (syn ο δείνα, ο τάδε): γιατί ο τάδε, ο δείνα και ο ~ έγιναν επαναστάτες; (Terzakis) | ο ~ και ο βήτα...