Why does a saving a customer's address in his address book not work in my store?

Magento 2 will not sane an address in an address book if it regarded it as incorrect.
It is the first screenshot case.
Moreover, Magento 2 uses a multi-level address validation (e.g., a phone number is validated in 7 places) so even if you cheat the system in some validation places, your address could be rejected in some other validation places.