A new car to you is not a brand new car.
Since production, this car may have sat in a dusty warehouse, travelled on trucks, trains etc, until it gets to you.
Also, depends on where the car was assembled.
So the paint on a new car is still a few weeks, may be months old.
So based on this logic, I would do a paper bag test on it to assess contamination situation and check for light scratches and swirls.
I would probably do a one stop polish and sealant on a new car as soon as I get my hands on it, after doing above tests.