So let's say that Samsung have a little server, it has all of the carrier and non carrier approved ota files there. Now the people with their note 8s hit software update, it goes to Samsung with the model number (unique to region etc) and the CSC which then tells it what carrier owns the phone. From this they send the update down. Now the CSC cannot be changed from inserting a sim card, you would have to flash a carrier ROm to change this or buy the phone from the carrier.
If I have a carrier SIM or not, I will always get the update relevant to my model and CSC.
I have confirmed this as my CSC hasn't changed, and I still have the international unlocked model number and my local (australia) non carrier CSC.
Further proved wrong, is that if I put a Verizon SIM in my phone, it would get me the sd version right? While I have the Exynos. So it would break my phone lol. Anyway I was in the U.S and used T-Mobile SIM and got no updates.