I think people are re-discovering/re-inventing Berners-Lee's semantic web and "linked data" descriptions (having the epiphany on their own) in part because Berners-Lee, for all his excitement, often fails at presenting the very basic idea, and I think it's because he takes the idea of a static URI for granted.

By using a URI like a globally-unique primary key - a symbolic link - into "the database of the web," in place of the content itself (not just as a pointer to a the next page page with cats) you can begin to use all of the web as the data set and something like XPath/XQuery as the query language.

Before any of that can happen, people need to really accept that URIs/URLs can't change their semantic content and rarely-if-ever go away. That's a big problem with the current approaches to displaying content: the references they generate are presumed to be forgettable.

A URN is still a pointer. An ISBN is not the book.

"Immutable URLs " Is a poor headline then.

It should read instead as "immutable content" since the OP intends to never have the content a URL points too to never be lost or changed