Like the other poster said, this is a problem with default values not encoding the birthday into the personnummer.

I think it also is important to remember the purpose of specific numbers. For instance I would argue a PN without the birthday would be strictly worse. With the current system (I only know the Swedish one, but assume it's the same) I only have to remember a 4 digit (because the number is bdate + unique 4 digits). If we would instead use completely random numbers I would have to remember at least an 8 digit number (and likely to be future proof you'd want at least 9 digits). Sure that's fine for myself (although I suspect some people already struggle with it), but then I also have to remember the numbers for my 2 kids and my partner and things become quickly annoying. Especially, because one doesn't use the numbers often enough that it becomes easy, but still often enough that it becomes annoying to look up, especially when one doesn't always cary their phone with them.