The way it works with physical printers is that there’s a very feint pattern in ink that the printer puts on every page, which is too feint to notice by eye. But if you know the dimensions of the pattern you can cut up all the tiles and add them together and get something that is clearly visible. So with a detailed scan, every printed piece of paper can be traced to the printer that printed it.

This is one of the reasons you can’t print in black and white without color on certain printers: if the pattern uses colors, then it can’t do its surveillance job without color ink, so it refuses to work at all.

A similar thing could be going on here. A pattern that looks like noise unless you know what to look for, embedded across the entire image.