Like mentioned before, these numbers have been imported from my phone on behalf of other people. I can assure you that my wife doesn't have her phone number in her facebook profile, yet there it is in the list. Likewise, I doubt my accountant has her PAs number on her profile yet there it is along side her FB profile along with an "add friend" link.
Like mentioned before, I'd be surprised that just because I accepted the T&Cs in app that this would be permissible under EU laws if the other party hadn't consented to FB retaining their number.
There are hundreds of people in my phone which are not listed from the link in the post, I only see people on my friends list who have their Facebook phone numbers shared there currently, or did at one time when it was imported into my phone book. Sounds more likely at one time your wife had her phone number pushed to / listed on Facebook and it was synced to your phone before she removed it.
Like mentioned before, I'd be surprised that just because I accepted the T&Cs in app that this would be permissible under EU laws if the other party hadn't consented to FB retaining their number.