Right, that's what I mean with "Facebook gives you the illusion that you can opt out of this data being public".

I recall when I still had Facebook, many people would randomly add you and pretend to be random people, sometimes famous, sometimes they "just want to be friends". I know most people have some settings along the lines of "no one except friends can see all this data". This is an issue, because people will add these "friends" and forget about these permissions. These "friends" can easily be attackers like these that suddenly have access to all your data. Hence the "illusion".

With a phonebook on the other hand, when you opt out, you've opted out.

Many people added you like that? Just asked a few people. No one gets many FB rando requests that aren’t super obviously fake. It isn’t that common.

I’ve had FB since 2007. Don’t recall there ever being a surge.

Prior to me becoming more privacy conscious I had 700+ "friends", of which less than 250 I actually ever met or was acquainted with. I recall one very specific interaction with one of those random requests of some person adding me and claiming to be Demi Lovato (I'd no idea who that was at the time) with their name spelled really oddly (I can't remember exactly, but they were trying to spell Demi Lovato but with random word or characters in between to make it look mildly like Demi's name, but not really). This interaction was somewhat of a wake-up call and that's when I realised I shouldn't be accepting random requests.

Afterwards my friend's list hovered around 150. These were family, close friends, less close friends, and acquaintances. I also had hundreds on my friend requests lists by the time I deleted my FB around 2015.