It should be noted that this app is temporary. The EU is aiming for a digital wallet app that you can store your identity documents in and that you can use to prove facts about those documents to third parties, in a way where the third party gets no extra information--just what you chose to disclose (e.g., just your age or just your country) and that cannot be used to link your real identity to your using the site even if the site and the government share logs (this is called unlinkability).

That will not be fully ready until around 2028. They wanted the age verification available earlier and that is this app. It does not have unlinkability.

Here's the expected timeline.

The first version of the wallet app is suppose to be out by the end of this year or early 2027. It will still not be unlinkable because Apple's Secure Enclave and Android's StrongBox don't support the cryptographic operations needed for the methods that will eventually be used for that, BBS+ anonymous credentials or ZKPs. There is a variant of BBS+ that can achieve unlinkability on existing phones, but unfortunately the hardware security modules (HSMs) currently used by government when they issue you your identity credentials cannot handle BBS#.

In 2027-2028 they are supposed to upgrade the government servers so they can support BBS# or zk-SNARK and update the wallet to use those, achieving unlinkability and anonymous age (and other data) verification.