Where does it say you have to follow through with data or erasure of users who can’t prove they are who they say they are? Both of those seem like the opposite of what you are supposed to do. I just checked the first result, and even the ICO [0] says

> [Your full name and address and any other details such as account number to help identify you]

[0] https://ico.org.uk/your-data-matters/your-right-to-get-your-...