In order to properly identify the family and code corresponding to a URL it also needs to check the path as multiple MediaWiki instances may be on the same domain. To do that it can either compare the path to index.php which is known as it's the same as the path to api.php (granted it may not be actually the same, I haven't checked and Family allows two different paths, but then we need to adjust Family.from_url). And that path is already known so that is fine. But most wikis on the interwiki map actually use the article path (e.g. en.wikipedia.org/wiki/$1) which is in Family.nicepath but due to T89451 we try to minimize the number of variables necessary and thus my patch is using APISite.article_path which does a request to the wiki to get the article path.

Now in it's own that is fine as you probably want a Site instance when you call Family.from_url. But unfortunately the APISite._cache_interwiki method creates a Site instance for every entry to actually cache it.