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The EFF has some info about the practice - https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots.
I imagine there are ways and means of obfuscating / anonymizing the dots such as blocking the printer from emitting them (e.g. an empty yellow cartridge that the printer perceives as full), modifying the firmware, using a burner printer, or using a mono laser jet.
As a side issue, most modern bank notes have a bunch of yellow circles integrated into the design on each side. They look random but they're in a recognisable pattern called a constellation that enables devices like copiers / scanners to recognize when people are trying to copy money or other financial instruments like checks.
The link you sent has a period at the end so it doesn't work when clicked.
It's a tracking dot