This issue came up with my Pria theme. I wanted a page template with the page title within a cover block, but with no way to include a cover image due to the dynamic nature of the root directory, had to make do with just giving the cover block a background color.

Also for the base theme of my WP Block Patterns site, I wanted the current number of preview themes do be displayed dynamically. Basically to avoid manually editing this every time in the page content.
As I have yet to learn how to develop blocks, my solution was using the Shortcode block on the page, with a call to a custom PHP shortcode that would return this number dynamically.

Themes adding their own shortcodes or creating their own blocks would obviously not be allowed in the org directory, so this new Pattern block would be the ideal solution.
Additionally the placeholder content can be changed by the user and would not be lost when switching themes.