Document that this only works for the page title, not for entity labels printed in twig

Clarified the title. By that clarification it seems just correct and expected. If someone uses the entity title instead of the page title, it should just work like that.

So if you run into this, don't use the entity title if you want the page title ;)

One possible workaround is, to use Twig Tweaks drupal_region() helper function to print the 'page_title'-region (if the theme has one). Twig Tweaks drupal_block() should also work.

This workaround might lead to caching conflicts, we'll see ...