What's the issue with WSJ? "people familiar with the matter" is standard lingo, means the journalist and editors have vetted the sources (multiple).

& many times the sources don't want to reveal their identity or go on record. A sort of tradeoff--to get the info they have to protect the source

"You may not talk to the media" is pretty standard language in US employee contracts so obviously these people don't want to fireable offenses on the front page of the newspaper.