I've been reading about Lodi apples since @WthrLady mentioned it. They are supposedly grown a lot in the South and it does look very similar to my apple and even matches the "late summer, early fall" harvest time. So I'm going to say it's probably a Lodi apple tree that was mismarked by the vendor.https://www.homefortheharvest.com/green-apples/
Try finding it here.