Editors say they forbid undercover operations:

“It is important that sources be aware that they are dealing with journalists,” said Tim Franklin, editor of The Sun in Baltimore. “It is not something that I feel comfortable with. This is a form of undercover journalism that, thankfully, went out of vogue in the early 1980’s.”

Presumably, the “early 1980s” represent some sort of ancient period in journalism wherein it didn’t almost universally suck.