Not sure what you mean. I wrote that there was never any proof required. Even the page you linked states that what is needed is only

> Date of birth (in the YYYY/MM/DD format)

> Country of birth

> NOTE: If “France” is selected in the Country of birth field, the registrants should also provide the city of birth and zip/postal code:

I was born on 1970-01-01 in 75001 Paris, France. There you are, an .fr registered.