The app knows the number of whatever phone it's installed on, it also knows all of the phone's contacts, and much more. The author agreed to share this information when he installed the Facebook app.

Perhaps the wrong number was an error on Facebook's part, perhaps it's something sinister, perhaps the author is just confused. We don't know, because the author of this article lacks a basic understanding of how the app, and Facebook, works. He didn't test his hypothesis, or even read the TOS, he just posted an article full of unfounded speculation. Again, if I were a betting man, I'd put my money on user error.

I'm not defending Facebook, they're horrible. I just think this article is garbage. Yes, that's harsh, but bad journalism has a much bigger impact on the world than my dumb comments.

I believe iOS doesn't share any information regarding phone number. Interesting point earlier I was using android, it could have got the right number if they wanted