Lauri Timmanee · Ben Mullins
--- a/core/modules/ckeditor5/src/HTMLRestrictions.php
+++ b/core/modules/ckeditor5/src/HTMLRestrictions.php
  }

  /**
-   * Gets a list of block-level elements.
+   * Gets a list of CKEditor 5's `$block` text container elements.
+   *
+   * This list is a hard coded list of known elements that CKEditor 5 uses as a
+   * `$block` text container elements. The elements listed here are registered
+   * with `inheritAllFrom: "$block"` to the CKEditor 5 schema.
+   *
+   * This group of elements is special because they allow text directly inside
+   * them. Also, these elements are allowed to be used for text styles that must
+   * applied to the wrapper, instead of applying them inline to the text. One
+   * concrete example of this is text alignment.
--- a/core/modules/ckeditor5/src/HTMLRestrictions.php
+++ b/core/modules/ckeditor5/src/HTMLRestrictions.php
  /**
-   * Gets a list of block-level elements.
+   * Gets a list of CKEditor 5's `$block` text container elements.
+   *
+   * This list is a hard coded list of known elements that CKEditor 5 uses as a
+   * `$block` text container elements. The elements listed here are registered
+   * with `inheritAllFrom: "$block"` to the CKEditor 5 schema.
+   *
+   * This group of elements is special because they allow text directly inside
+   * them. Also, these elements are allowed to be used for text styles that must
+   * applied to the wrapper, instead of applying them inline to the text. One
+   * concrete example of this is text alignment.
+   *
+   * This list excludes some special case text container elements like
+   * `<caption>` that are not fully implementing the $block text container
+   * interface.
--- a/core/modules/ckeditor5/tests/src/Kernel/SmartDefaultSettingsTest.php
+++ b/core/modules/ckeditor5/tests/src/Kernel/SmartDefaultSettingsTest.php
        '<h4 class="text-align-center text-align-justify">',
        '<h5 class="text-align-center text-align-justify">',
        '<h6 class="text-align-center text-align-justify">',
-        '<dl class="text-align-center text-align-justify">',
-        '<dd class="text-align-center text-align-justify">',
-        '<blockquote class="text-align-center text-align-justify">',
-        '<ul class="text-align-center text-align-justify">',
-        '<ol class="text-align-center text-align-justify">',
+        '<li class="text-align-center text-align-justify">',