Perhaps rr808 is referring to AI upscaling. As in, are these 139 proper megapixels or upreased to that size?
It's made from over 90,000 individual images that have been stitched/combined together. I'm not the original photographer so I can't comment on his process, but I think it would be silly to use upscaling (AI or otherwise) when your starting data set likely contains multiple gigapixels.