What Google calls "Core Updates" nowadays are not anywhere near the same thing as they used to be. Core updates now are when a newly expanded knowledge graph (which has been tested in smaller doses for a while) is injected into the primary database for general consumption. Sure, there are other things that get updated, but that's the primary element. Among the first of these was the "Medic" update - one which included a knowledge graph that had a lot of medical, science and YMYL type information in it. (Hence the name). Another big one was last June's update which had a lot of "news" and "fact based" sites - why, if Google allowed name giving by Barry, it would have been called something like "The Fake News" update). Keep in mind, Google is very specific in what they call these. The "Algo" updates almost daily - and, in some cases, updates by the minute as certain things occur in the world. These announced updates are always called "Core" updates and it's less about updating the algorithm and more about updating the core of knowledge Google has about entities and their attributes which is used by the algo to rank the pages.