IDIN is set up by all the Dutch banks. You check in via your own bank using an IDIN link. IDIN will do an age-check to verify that you're 18 or older. IDIN can verify age, name, address and contact info. You need a bank account, and the bank has checked your identity and age, so this is guaranteed to work.
Maybe you don't want that the bank knows that you visit a porn website, but that's another question.
From a logistics one, devices can be shared and it is very easy to share to a minor (which is what theses laws supposedly target). Or have multiple accounts on one device.it seems like a lot of work for less results..