Anything before the sensors (including intakes) has a potential issue with warranty.
As far as the hood struts, locking lugs, spacers, and tow hook, it's all good.
Yes, this has happened quite often, and not just with GT-R's. I've seen G35's with superchargers, IS's with a bunch o' stuff, and even Porsches that come with an aftermarket steering wheel (including other parts) on them, and raise the numbers accordingly.
So to answer your question - yes, it's not uncommon. But I will add, that I agree with your 'passing' of this one.
yes it is a demo car for the owner, its baker nissan in houston. their tech and owners participate in alot of the car meets they have down in the houston area. just advertising for them. they also have a nissan 370z with the whole amuse kit.