I am an enumerator for the census here in WS and yes we do ask for phone numbers. I have asked people for information about their neighbors because I was unable to contact them. And if you do give us the needed information, we do need to have a record of who we got in from, including an address and phone number.
If you have any questions about anyone who has come to your door and anything you’ve received in the mail, go to census.gov and direct your question to your local office.