include_vars: elaborate description of dir option (#52022)

based on work of thecjharries

Additional behavior documentation of 'dir' option in include_vars.

Fixes: #31761

lib/ansible/modules/utilities/logic/include_vars.py

@@ -34,7 +34,8 @@ options:
     version_added: "2.2"
     description:
       - The directory name from which the variables should be loaded.
-      - If the path is relative, it will look for the file in vars/ subdirectory of a role or relative to playbook.
+      - If the path is relative and the task is inside a role, it will look inside the role's vars/ subdirectory.
+      - If the path is relative and not inside a role, it will be parsed relative to the playbook.
   name:
     version_added: "2.2"
     description: