Earlier quoted context omitted.
Right now it's very easy to see, the companies are not hiding it at all. They send the data to third-party trackers straight from their website or application.
Disqus loads a million external resources That’s so stupid, why not just take your OWN cookie and use it in the backend to send to all these resources, proxying through your own server or having a CNAME for theirs under your domain?
The CNAME practice is becoming more and more common. See https://blog.apnic.net/2020/08/04/characterizing-cname-cloak... or https://medium.com/nextdns/cname-cloaking-the-dangerous-disg... or https://www.laquadrature.net/2020/10/05/le-deguisement-des-t...
I think proxying or doing it server side only will be implemented later when these people will be forced to hide to save their shitty business model.