In social networks an ad looks like a post. It does not arrive over its own address but sits inside the same page content — and that changes how you get rid of it.
Because they have no request of their own, they cannot be caught before loading. AdSilence recognises them by the structure of the page and takes them out of view. That is a difference: the loading is not prevented, but afterwards they are gone from sight.
The network does not only measure at home. Measurement points from the same provider sit on thousands of other sites — and those are perfectly ordinary requests. AdSilence catches them like any other tracker.
The structure of a feed is reworked regularly, and cosmetic rules then have to follow. If a post is left standing once, the extension is not broken — the rule is older than the page.