The website operator is deciding what data is sent to Facebook my implementing the button. How are they not a (joint) data controller in that respect? BTW, th

The website operator is deciding what data is sent to Facebook my implementing the button. How are they not a (joint) data controller in that respect? BTW, the article didn't actually spell this out, but the website operator's "responsibility is, however, limited to the operation or the set of personal data processing operations for which it actually determines the purposes and means, namely the collection and communication by transmission of the data in question." (translated using Google Translate from the French-language version of the judgment)