I'm not sure how successful it is in that regard. Just browser fingerprinting is enough to track most people; cookies and third party connections are not essential.
It prevents ad companies from fingerprinting you, you never make the connection to seedy-ad-company-X, you only make the connection to facebook/nyt/WaPo etc
3rd-party CSS. I.e., if the page includes CSS from an ad network, the network gets the request and can track it. Basically using CSS instead of a 1px tracking bug.
One of the many shitty, underhanded methods these companies use to track people without their knowledge or consent. I will shed no tears for these companies when they go bankrupt as people push back against their methods.
I understand now, but the idea of CSS in this is what threw me off. This is valid for any file that the computer makes a request for, if queries are attached to it.
https://wiki.mozilla.org/Fingerprinting