A phone number (or email) is not strictly necessary [1]. Some banks do indeed require it for the Wero account setup, which in my opinion is a mistake. You only need the additional identifiers if you want to look up other Wero users using your phone's address book to send money P2P without using a QR code.

It's not possible to register the same phone number (or email) at two banks simultaneously. The last registration wins and the associated bank account will switch on the backend when you try this.

Also, EU bureaucrats have little to do with it. Wero is the third attempt by a subset of private European banks to establish a new pan-European payment network.

[1] https://support.wero-wallet.eu/hc/en-us/articles/25599201237...