So, as a speech act, when we say "What's the update on the shelf?", we are not interested in your specific furniture, but you should read it as "We are listening to the podcast and we are part of your in-group of ideas."

@michaelhobbes.bsky.social & @notalawyer.bsky.social
On the longevity of The Shelf:
Similar to kids saying 6-7, it's a meme for us listeners to identify ourselves to you and to one another. Linguistically speaking it has become a shibboleth which is why it persisted after you stopped mentioning it.