A list of email addresses "which can be matched to signed-in users" - it is not clear if the list will have to be gmail addresses matching the logged in users?

A list of email addresses "which can be matched to signed-in users" - it is not clear if the list will have to be gmail addresses matching the logged in users? I'd assume so, unless Google is maintaining links between people's google email addresses and other addresses they might use (eg. multiple email boxes being used on the same phone)to make a match, which is also plausible.