docs(template-syntax): correct ref var scope per #2458 (#2602)

closes #2458

public/docs/ts/latest/guide/template-syntax.jade

@@ -1244,9 +1244,13 @@ figure.image-display
 :marked
   ### Referencing a template reference variable
 
-  We can reference a template reference variable on the same element, on a sibling element, or on
-  any child elements.
+  We can refer to a template reference variable _anywhere_ in the current template.
+.l-sub-section
+  :marked
+    Do not define the same variable name more than once in the same template.
+    The runtime value will be unpredictable.
 
+:marked
   Here are two other examples of creating and consuming a Template reference variable:
 +makeExample('template-syntax/ts/app/app.component.html', 'ref-phone')(format=".")
 :marked