If you block Contacts access on your phone (iOS/Android) can Faceboook still access your contacts ? Are you aware of any loopholes that lets Facebook access someone's contacts ?
There was a case not so long ago where unrelated patients of a psychiatrist were suggested as friend to each other. The only possible link is that they all had the psychiatrist in their contact or vice-versa. The friending suggestion by itself was an outing of private medical information.
Its creepy, and slightly disturbing to realise just how much effort they are putting in to mapping out your life and acquaintances even when you try to prevent it.
Although I recall a comment by a Facebook engineer about how they link users based on their IP addresses. So if you and your coworker are connected to the same WiFi at work Facebook can easily figure out that you both work at the same place.