These are used in zero-knowledge proofs (ZKP) – a way for two parties to validate that one of them asserts a fact without learning what that fact is in the process (this is super cool stuff). Users can send their subcredentials to a third party, who can use a ZKP to validate them without learning anything else about the user – so you could prove your age (or even just prove that you are over 18 without disclosing your age at all) without disclosing your identity.
All the arguments against ZKP on the following paragraphs misunderstand the way the state and intergovernmental institutions, and the rule of law work in the EU. Many EU countries already have digital identity providers that are used every day by their citizens. I think very few people are arguing in favor of dismantling them.
From your source:
All the arguments against ZKP on the following paragraphs misunderstand the way the state and intergovernmental institutions, and the rule of law work in the EU. Many EU countries already have digital identity providers that are used every day by their citizens. I think very few people are arguing in favor of dismantling them.