An update on my previous note, on consulting with an ex-Makani engineer I was able to open the case lid without damaging the part, and I can confirm that it has eight dies, not nine. I was initially mislead by the Rdson and Cgs being lower than the expected values for eight, but they don't give upper and lower limits in the datasheet so it seems like the dies are well below the typical Rdson specified in the datasheet.