docs($compile): clarify to which element scope isolation applies

Closes #13556

src/ng/compile.js

@@ -277,10 +277,12 @@
  * the directive's element. If multiple directives on the same element request a new scope,
  * only one new scope is created.
  *
- * * **`{...}` (an object hash):** A new "isolate" scope is created for the directive's element. The
- * 'isolate' scope differs from normal scope in that it does not prototypically inherit from its parent
- * scope. This is useful when creating reusable components, which should not accidentally read or modify
- * data in the parent scope.
+ * * **`{...}` (an object hash):** A new "isolate" scope is created for the directive's template.
+ * The 'isolate' scope differs from normal scope in that it does not prototypically
+ * inherit from its parent scope. This is useful when creating reusable components, which should not
+ * accidentally read or modify data in the parent scope. Note that an isolate scope
+ * directive without a `template` or `templateUrl` will not apply the isolate scope
+ * to its children elements.
  *
  * The 'isolate' scope object hash defines a set of local scope properties derived from attributes on the
  * directive's element. These local properties are useful for aliasing values for templates. The keys in