Citation needed? Facebook gets revenue from their ad network, which is used by European business customers and targets European users. Therefore they need to comply with European law.

I've never heard of this before, is it a part of GDPR?

The Facebook Europeans use is very much an EU company.

https://boingboing.net/2017/11/08/involuntary-profiling.html

"Facebook is well understood as being a major customer of third-party data-brokers, who compile huge dossiers on people based on their spending, internet and phone usage, employment history and so on. In addition, Facebook encourages users to upload their entire address books to the system to "find your friends," and users generally don't appreciate that they may be leaking sensitive information, including nicknames, private numbers, and connections to the system.

Facebook mines this data to create "shadow profiles" of its billions of users. These are profiles that are filled with data about you that you have never consciously provided to the system -- data mined from third parties, including your friends, but also those spooky data-brokers. Facebook's shadow profile system was first confirmed in 2013 when it accidentally leaked users' shadow profiles to them along with their own data, something the company says it will never do again out of (ironic) respect for the privacy of the people who provided the data that goes into your shadow profile.

Facebook's shadow profiles are involuntary and there's no opt-out. Facebook has shadow profiles on people who don't use the service. For example, even though I'm not a Facebook user, multiple people have uploaded their address books containing my email and phone number to the system, allowing Facebook to create a profile of my contacts by looking at who lists me as a contact."