From the actual opinion: "Oklahoma replies that its situation is different because the affected population here is large and many of its residents will be surprised to find out they have been living in Indian country this whole time. But we imagine some members of the 1832 Creek Tribe would be just as surprised to find them there."
Damn, nice shade, Gorsuch!
https://www.supremecourt.gov/opinions/19pdf/18-9526_9okb.pdf