I think this notion that Ester oil is the factory-fill is highly doubtful. I know, I know, I've heard the argument before: Nissan made this oil for this engine, so of course it comes from the factory filled with it. Per one of your previous posts in this thread:
Sounds reasonable, except for two things. First off, Ester oil is recommended, not required, and most corporations -- especially Nissan -- have a habit of doing what's minimally required only. Why? Because they're bean-counting tightwads (just look at how they've handled the oil-cooler issue). So I don't think we can assume that a company will fill their cars with a specific oil even if they specifically designed that oil for that car. This is especially true if said oil is more costly than the regular stuff they use. I know, that just doesn't seem right. But I've seen stranger decisions made, especially whenever there are a few bucks to be saved.
More significant, however, is the TSB for VVEL noise for the G37. The G37 has the exact same engine, so one would expect it to come with Ester oil as factory-fill as well, right? After all, Nissan designed the oil for this engine. Yet, on the Infiniti side of the house, there's a TSB for the issue of valve noise ( ITB08-028a - Noise from bank 2 VVEL actuator). Guess what the TSB says the fix is? It's a two-parter: A software update, plus changing the oil over to Ester oil! Now, let's think about this. How would it make sense for part of the fix to be changing the oil over to Ester oil if it already came from the factory with the stuff in the engine? I mean c'mon, let's use a little common-sense deduction here. In spite of designing this oil for this engine, they're filling these engines up with the cheap stuff at the factory!
I do realize that there's always a chance that they're doing something different for the 370Z vs. what they're doing for the G37. Like maybe they're using Ester oil as the factory-fill for the Z but holding out on the G for some bizarre reason. That's why I chose to characterize it as highly doubtful, vs. using the word "impossible." But I don't think it's slam-dunk obvious that they're using Ester oil for factory-fill either, as you seem to think it to be. I would be quite surprised -- pleasantly so -- if they're using the good stuff for the factory-fill.
The TSB is attached below. You can also read more about this TSB at myg37.com
ITB08-028a - Noise from bank 2 VVEL actuator (amended 9/3/08) - MyG37