The "short" 3SG pronouns are subject to distributional restrictions, which suggest that these are dependent pronouns. In particular, 3SG o (used by all speakers) is not used emphatically, does not appear in dislocated position or in focus, and cannot be conjoined or modified, in contrast with the full form ori, which is not restricted in this manner. Furthermore, the 3SG form a, whose use is idiosyncratically restricted to a single speaker, is used only as non-emphatic subject pronoun.
Source: Kouwenberg 1994a: 662
Source: Kouwenberg 1994a: 649