Earlier quoted context omitted.
In this particular case, it would be harder to produce a fake signature from a non-existent person if the signatures in questions were digital and backed by a national identity number. The kind of that I'm submitting when signing documents at work.
Aside from the fact the entry in question was added to the list almost two decades ago, it’s naive to assume that people would only be put on these lists if they have a verified identity number. If that was a rule, the easier rule of requiring a birth date would already have helped. Because while not everyone has a national ID number, pretty much everyone has a birth date.
I do not know how are they handled, but they probably get assigned one plausible date and it probably depends on the country.
In a sense, a birth date can be just as much an assigned number as an ID is. An ID can also have a checksum in it, potentially even a cryptographic one that only government can sign.