diff --git a/core/lib/Drupal/Component/Scaffold/Handler.php b/core/lib/Drupal/Component/Scaffold/Handler.php
index e59c53c9ad..4ef96aa2d5 100644
--- a/core/lib/Drupal/Component/Scaffold/Handler.php
+++ b/core/lib/Drupal/Component/Scaffold/Handler.php
@@ -147,7 +147,7 @@ public function scaffold() {
     // Fail fast if the required 'web-root' location is not set in composer.json.
     $webRoot = $this->manageOptions->getOptions()->getLocation('web-root');
     if (!$webRoot) {
-      throw new \RuntimeException("The extra.composer-scaffold.location.web-root is not set in the project's composer.json.");
+      throw new \RuntimeException("The extra.composer-scaffold.location.web-root configuration is not set in the project's composer.json.");
     }
 
     // Call any pre-scaffold scripts that may be defined.
diff --git a/core/lib/Drupal/Component/Scaffold/Operations/OperationCollection.php b/core/lib/Drupal/Component/Scaffold/Operations/OperationCollection.php
index ce2c00ddfd..8076f6a717 100644
--- a/core/lib/Drupal/Component/Scaffold/Operations/OperationCollection.php
+++ b/core/lib/Drupal/Component/Scaffold/Operations/OperationCollection.php
@@ -34,11 +34,10 @@ public function __construct(IOInterface $io) {
   /**
    * Finds the package name that provides the scaffold file.
    *
-   * Given the list of all scaffold file info objects, return the package that
-   * provides the scaffold file info for the scaffold file that will be placed
-   * at the destination that this scaffold file would be placed at. Note that
-   * this will be the same as $scaffold_file->packageName() unless this scaffold
-   * file has been overridden or removed by some other package.
+   * This will usually be $scaffold_file->packageName(), unless there are
+   * multiple scaffold files with the same destination path. In the case
+   * that there are multiple scaffold files, the name of the last package
+   * that provided a scaffold file at that path will be returned.
    *
    * @param \Drupal\Component\Scaffold\ScaffoldFileInfo[] $list_of_scaffold_files
    *   Associative array containing destination => operation mappings.
@@ -53,7 +52,7 @@ protected function findProvidingPackage(array $list_of_scaffold_files, ScaffoldF
     // just to be sure that it really is.
     $dest_rel_path = $scaffold_file->destination()->relativePath();
     if (!array_key_exists($dest_rel_path, $list_of_scaffold_files)) {
-      throw new \RuntimeException("Scaffold file not found in list of all scaffold files.");
+      throw new \RuntimeException("Scaffold file $dest_rel_path not found in list of all scaffold files.");
     }
     return $list_of_scaffold_files[$dest_rel_path]->packageName();
   }
diff --git a/core/lib/Drupal/Component/Scaffold/Plugin.php b/core/lib/Drupal/Component/Scaffold/Plugin.php
index bf91dbae3a..71d049eccf 100644
--- a/core/lib/Drupal/Component/Scaffold/Plugin.php
+++ b/core/lib/Drupal/Component/Scaffold/Plugin.php
@@ -30,9 +30,9 @@ class Plugin implements PluginInterface, EventSubscriberInterface, Capable {
    * {@inheritdoc}
    */
   public function activate(Composer $composer, IOInterface $io) {
-    // We use a separate PluginScripts object. This way we separate
-    // functionality and also avoid some debug issues with the plugin being
-    // copied on initialisation.
+    // We use a Handler object to separate the main functionality
+    // of this plugin from the Composer API. This also avoids some
+    // debug issues with the plugin being copied on initialisation.
     // @see \Composer\Plugin\PluginManager::registerPackage()
     $this->handler = new Handler($composer, $io);
   }
diff --git a/core/tests/Drupal/Tests/Component/Scaffold/Functional/ScaffoldTest.php b/core/tests/Drupal/Tests/Component/Scaffold/Functional/ScaffoldTest.php
index a5b88a1eb0..e272dedc47 100644
--- a/core/tests/Drupal/Tests/Component/Scaffold/Functional/ScaffoldTest.php
+++ b/core/tests/Drupal/Tests/Component/Scaffold/Functional/ScaffoldTest.php
@@ -181,8 +181,8 @@ public function testProjectWithoutWebRoot() {
     $is_link = FALSE;
     $relocated_docroot = FALSE;
 
-    $this->expectException(\Exception::class);
-    $this->expectExceptionMessage("The extra.composer-scaffold.location.web-root is not set in the project's composer.json.");
+    $this->expectException(\RuntimeException::class);
+    $this->expectExceptionMessage("The extra.composer-scaffold.location.web-root configuration is not set in the project's composer.json.");
 
     list($docroot, $scaffoldOutput) = $this->scaffoldSut($fixture_name, $is_link, $relocated_docroot);
   }