Ooookay. Thanks for broadening my horizon.
Again, I only know about Germany, but we have strict rules to reject any paper ballot that could be traced to an individual voter. Mostly to prevent buying votes (for which there are easier paths at mail-in votes that don't require a colluding election helper), but … if even rumours were coming up that "the government" could use "those yellow printer dots" to track who's voting for whom, there would be trouble.
(There's even a regular conspiracy theory, wide spread enough so it's part of every election helper training, about the cut corner in all empty ballots - which is solely so even blind people can vote on exactly the same paper ballots as the rest)