It's a cloud reflection. I think people are generally attributing a little bit much in terms of what "upscaling" really does. Especially on an iPhone, which I used, that does not do traditional "upscaling."
Still, that's very apparent on large ad posters Apple used to make "shot with an iPhone", a zoomed in photo looks like it consists of irregular patches of solid colour, not pixels. That's what I called upscaling, that's what my old Honour used to do to photos when it fell flat on actually capturing the details, and maybe that's what others meant, too.