I understood the MoV authors (Part 9) think of it as a species complex, suggesting there are two major forms at least with male and female versions. The forewing pattern suggested Proteuxoa capularis to me, but clearly it;s not that species.
On page 2/4 of their notes for A. porphrycollis (Part 9, Moths of Victoria) the authors say 'DNA analysis' has confirmed there are two species which have been given the name 'Agrotis porphrycollis'. I think this specimen looks more like the male of first 'species' of the two they illustrate for A. porphrycollis on page 1/4.