[manigandham]

Yes, Facebook and Google both learn from your actions on their site, including the outbound links. They can infer interests from that.

However most sites, like in your example, also include their analytics tools and directly send them data. Ecommerce stores will often report conversions with your email address to G/FB so that you can be targeted for ads as a return customer. A lot of the data collection is done like this where other businesses do the actual collecting and sending.

Mobile is much worse with privacy. The web has to deal with constantly changing security rules, limited APIs, and purged data. On mobile, most usage is in apps which have strong identifiers that never change, and access to far more system level data and APIs. They can - and do - leak far more data. That's why you have expose articles that show that people were tracked by location for entire weeks at a time, which is not possible at all with websites.

FloC is only for anonymous situations. If you're already logged into G/FB and are on their sites, or accessing their resources as a 3rd-party, then they already know you are. FLoC and similar tech is used for when you identity isn't known, and then your browser provides rough categories of interests based on what sites you saw before. Remember the ultimate control over privacy is you and what data you willingly send. Many people login and post everything themselves, thereby being their own worst enemy when it comes to privacy.