Yes, Hyundai Motor America buys batteries in the US from Interstate (or whomever) and puts their part number on them and distributes them to Hyundai dealers. What I am saying is that they don't use Interstate batteries at the factory in South Korea.
Interstate is owned by Johnson Controls, which also supplies batteries for many other brands such as AutoZone, Advance Auto Parts, and many others.
I don't know for sure, but would wonder if the INTERSTATE BATTERY-H8-100AH is an AGM battery, as was the Platinum one from AutoZone that you are comparing it to. Based on the price, it seem unlikely. A more fair comparison would be the Gold batteries from AutoZone. In fact, the Interstate battery sold by the dealer may be more like the Silver AutoZone.
If your Genesis is 7 years old, I don't believe the OEM battery was AGM (but the 2nd Generation Genesis starting in MY 2016 and the 2017+ G80 do use AGM as OEM, part number 37110-B1100).
The online price for Hyundai part number 37110-B1100 (AGM battery) is $480.94, but it is probably an H9 battery and not an H8 .