I think you're right, and it's not just those looking at Platonism afar... I was reading up on the tradition in an encyclopedia of religion, which you think would be authoritative, and it very distinctly referred to Neoplatonism as "dualistic," and I did a double-take.

(On the other hand, it referred to the soul as "amphibious"—living in two worlds as it does—which I thought was just the best.)