To survive, the NE needs a constant flow of confidential info (tips, if you will). And they need to protect those sources. Suppose it was Trump. Would the NE say, "Yep, it was Trump. Good guess, Ted."
No, it isn't meaningless. NE didn't give up their source, they just eliminated Trump as a possible source. If Trump was the source, the National Enquirer would have kept quiet about it.
Except lots of proof that it was Rubio’s people.