My guess here is that the image isn't fake per se, but it's missing the context.
I'm guessing the "original" is much higher resolution than 16MP. Google Photos' "high quality" being always limited to 16MP, my guess is that the comparison shot is between what I'm guessing at least 60MP or even 100MP image vs (downsampled) 16MP.
For more sane comparison of what "high quality" does, I find:
i.e. unless you have a camera with substantially higher resolution than 16MP or you're a professional photograph (or equivalent amateur who cares about subtle pixel level details), high quality is good enough for all casual photographers , which is basically 99% of us including myself.