This paper concerns the unusual argument marking pattern in Nias Selatan (Austronesian; Indonesia). As discussed in both descriptive and theoretical works, Nias exhibits a mutation system that appears to track absolutive grammatical role. Subsequently, such works, notably Baker 2015, have hypothesized that Nias' mutation system is the realization of a typologically unusual 'marked absolutive' case system. In this paper, I argue against this hypothesis from both an empirical and theoretical standpoint. I suggest an alternative hypothesis, where mutation is a regular phonological process. Further, I propose that the surface pattern that initially motivated the mutation-as-case hypothesis is due to the interaction of this regular phonological process with independent syntactic factors that affect whether a given nominal is in a mutation triggering context.