He has been with Nissan for about 15 years. He said that the oil that comes in them is just factory Nissan trans oil. It is not any special break in fluid. It is recommend that you change it for a high quality synthetic if you plan on beating on the transmission. I did change to synthetic pretty early on with mine and it still has the input shaft noise. It came up well after I made the change. Only about 20k miles on it at this time. Never gets worse or causes any problems. Just a little noise.
My old transmission did the same thing after I began doing mountain runs and track events. So I would say the fluid theory is.......not proven yet.