In Samarin (1967) I made the mistake of considering ni (with high tone) as both the "restrictive" (now called the "determinant", i.e. definite article) and a pronoun. The latter is ni with a mid tone, which has a logophoric function.
In the 1990s I found that the determinant is being used as a pronoun for inanimate objects since lo 3SG is used for human beings. But as early as the 1950s one could say (and can still say) ni laa [DET FOC] 'That's it.'
The co-occurrence of ni so as in Example 99 is common; they clearly have two functions.
Source: Samarin 1967: 63
Source: Samarin 1967: 64
Source: Taber and Samarin 1965: 100