PR# 13902 ECF: same cluster tag at different nested levels

When I try to compile my application with this ECF file:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<?xml version="1.0" encoding="ISO-8859-1"?>
<system xmlns="http://www.eiffel.com/developers/xml/configuration-1-3-0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.eiffel.com/developers/xml/configuration-1-3-0 http://www.eiffel.com/developers/xml/configuration-1-3-0.xsd" name="app">
  <target name="app">
    <root class="APP" feature="make"/>
    <library name="base" location="${ISE_EIFFEL}/library/base/base.ecf" readonly="true"/>
    <cluster name="foo" location="foo_path">
      <cluster name="bar" location="$|bar"/>
    </cluster>
    <cluster name="bar" location="bar_path"/>
  </target>
</system>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I get this error:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Parse error in app.ecf (line 9, column 42): Invalid cluster tag there is
already a group with the name bar.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

First, there is a comma or a period missing in the error message between
tag and there.

What I don't understand is why this is an error in ECF. The two clusters
with name "bar" are not at the same level, so there should not be any
ambiguity. We can reference the top level cluster using the name "bar"
and the nested cluster using the name "foo/bar" (other something like 
that).