Update documentation to be clearer on how marshalling works

Document that setters will not be triggered, and fields will not be
marked dirty if the value is an identical scalar and an entity is
updated.

src/ORM/Table.php

@@ -2490,6 +2490,11 @@ class Table implements RepositoryInterface, EventListenerInterface, EventDispatc
      *
      * You can use the `Model.beforeMarshal` event to modify request data
      * before it is converted into entities.
+     *
+     * When patching scalar values (null/booleans/string/integer/float), if the property
+     * presently has an identical value, the setter will not be called, and the
+     * property will not be marked as dirty. This is an optimization to prevent unnecessary field
+     * updates when persisting entities.
      */
     public function patchEntity(EntityInterface $entity, array $data, array $options = [])
     {