Couldn't that be defeated by a preprocessing step that inserts yellow dots at every grid position on the printout? If the extra dots were aligned correctly, I don't see how someone could recover the encoded information.
Someone could probably create a printer driver that does that automatically. It probably would need some calibration to work, though.
I was briefly trying to do that as part of our project about this but I didn't figure out the proper pixel size and offset, nor whether you can use a fixed offset relative to the edge of the page or whether the printer tries to defeat this by slightly randomizing the offsets. I hope someone will figure it out.
There's an additional challenge that some more recent printers often use a different watermarking technique whose details have never been documented.
Someone could probably create a printer driver that does that automatically. It probably would need some calibration to work, though.