FTR - I have and '07 with the 19" Nismo and 245/40/19 and my rear passenger wheel rubs when people are in the back (including just 2 light kids).
I've actually loaded up the trunk with weights one time and had people sit in the back so I can see the clearance while the car was still and it seems to be clearing the fender by an RCH. And I would imagine that as bad as the rubbing can be sometimes that there would be some noticable damage to the fender or the tire, which there isn't.
There is also a bolt with a plastic cap that at the top center of the wheel that holds the wheel well liner in place. It's possible that the offset is enough that the stock narrower tires just clears it but the wider 245s just contact it enough. I've removed the plastic cap, but the leaving the exposed bolt worries me more with making tire contact than the plastic cap.
I see all these Maximas with much larger tires and wheels than the 245/40/19 without issues and it baffles me.
I've actually brought this to the dealer one time and they were useless. So useless that they actually tried to compare the offset and wheel gap to an Altima coupe with the Nismo's in the showroom.

And of course, they couldn't reproduce the noise.