[carrolldunham]

It might certainly be possible to come up with a ML approach that was able to discover details in the image that were entirely lost on even highly trained human viewers.

This is certainly a fair point but that's a different question from recreating the real details from a compressed image where that data is just gone. There are an infinity of images that you can downsample to say, a 2 pixel by 2 pixel image. You can make an algorithm to produce candidate sources but not distinguish between which was the actual source. The data processing inequality is the formal result covering this. So where you are saying this algorithm doesn't do it, it's moot because it can't be done