It isn't all just journos making things up. I think most of the rumors of specific players come from agents and clubs using the media to play games and further their own narrative. An agent wants to raise the profile of their client, get a new contract, etc. A selling club has a team interested, but wants a bigger fee, so they float other clubs' interest. A buying club wants the world to think that they beat out a bigger club for a player, etc.
And sometimes those sources are giving information that they believe is correct, but they are in the dark on something (Morata's red hair, anyone?). So even someone as ITK as the actual player can be wrong.
Higher tier journos are probably getting info that has more to it than lower tier journos, but their sources could also be blowing smoke or just plain wrong.