Abusing the framebuffer contents to do convincing-unless-you-stare-closely-at-them reflections is a time-honored tradition stretching back to the early 2000s. Nintendo pulls off this effect a couple of times in this shot:
From the username & submission history, I'm guessing you're the author of noclip.website & the associated youtube videos explaining various graphics effects in SMG/WW. Love your content!
Is that website supposed to work on mobile? I get a couple of microscopic icons on a black background and a message about a non-responsive script after a few minutes.
https://noclip.website/#smg/HeavensDoorGalaxy;ShareData=AY,m...