Because NYCFC is not a European club, but is backed by big money and can still be a name-drop of international proportions. If you say that a big European team is interested in a player, or even a middle-rank team such as Stoke, or Lille, or Getafe, then every local team back in South America is going to know that they have no chance to match the wages and the European football and that the player is already gone. NYCFC is not going to be signing him as a DP, which throws out the very real chance that we could be outbid for his services, and with all due respect MLS is not yet quite at the level where a player offered a low wage to play there is going to absolutely consider it a far better alternative than receiving a far higher wage to stay in the same league. Also, NYCFC's links to CFG mean that the article will get far more coverage than just claiming that someone like Boca Juniors or Sao Paulo are interested.
Of course, it could still be a genuine truth. I'm not discounting that theory, I've just learned to be very sceptical of stories like this which come out of left-field.