Attribute subtyping, clarification request

While we're on the subject of attributes and attribute subtypes:

If I understand correctly, displayName;lang-de is a subtype of 
displayName, rather than an instance of it, so that it would be 
possible to have several displayName assertions, each one in a 
different language, without violating the single-value property of the 
attribute type.

It should also be possible to have displayName;lang-fr;lang-es if the 
spanish and french names were identical, right?

But then the rules don't seem to prevent the above from being combined 
with displayName;lang-fr and displayName;lang-es as individual 
assertions, in which case a search requesting the displayName;lang-es 
attribute type would actually (surprisingly) return two assertions. Or 
am I missing something?

Rici