Здорово. А подскажете, где искать формальные требования к документам, чтобы если что поспорить с теми, кто требует? Или может есть прям пруфлинк?

В вашем случае тут: https://ind.nl/en/translation-and-legalisation-of-documents

For most documents, the IND does not check the date on which it was issued and legalised. The details of these documents are definite. For example, a birth certificate, marriage certificate or death certificate. The requirement is that the document has been legalised for use in the Netherlands. The IND accepts a single status declaration only if it is not older than 6 months.