Problem/Motivation
I am installing Drupal via a Drush site install command, and then applying recipes to it for further configuration. A recipe is installing Claro as the backend theme. After installation, blocks have been copied from the frontend theme towards the claro theme, where they shouldn't have been.
This had been fixed up until Drupal 11.2 - via the issue #3182716: block_theme_initialize should not create blocks during config sync. But since using Drupal 11.3.0, this appears again.
The only change I see is that the logic has been moved towards an OOP hook, instead of a regular module hook in D11.2.