The Goodreads account is, I believe, reflective of the AskHistorians booklist. This list is compiled and maintained by our flaired users. To speak directly to your question, this means that the Goodreads list should be updated when the main booklist is updated.

Now, when is the main booklist updated? Sporadically. Basically, the main booklist is updated whenever a flair or group of flairs volunteers their time to do so. Sometimes this is a lone flair adding a single book, but sometimes it is a large coordinated project by a lot of flairs. An example of the latter type of revision is the East Asia booklist which was the subject of a massive and comprehensive reworking in the not too distant past.

The AH Goodreads account has been on hiatus for a few years now, reflecting shifts in the composition and priorities of the mod team since it was first made. This means that it hasn't been updated in a while, but we know that some people still get use out of the content that was already compiled, so we don't want to take it down or anything.

We definitely wouldn't rule out reactivating it again in the future (especially if it becomes clear that it would be something a large number of users want), but it's not really on our radar as a priority at the moment. This kind of thing - similarly to keeping our booklist regularly updated - requires a surprising amount of attention and drive to keep going, since obviously no single person is able to just do it by themselves for the entirety of human history.