Earlier quoted context omitted.
Anonymous sources that are quoted directly are known to the journalists ; their identity is only concealed from readers. This is about anonymously passing information for further investigation.
So you're saying that no journalist would accept a tip from someone who will not identify themselves?
You may be thinking of "unnamed sources" or "anonymous sources". Those people may be quoted on a factual basis, but the reporter has an obligation to obtain the same kind of confirmation of their information as any other investigative lead.