Test case:

=== Article text ===
Lorem ipsum<ref name="expl_A" group="n" />
===Explanatory notes section===
<references group="n">
{{#tag:ref
|BBBB
|group="n"|name="expl_B"}}
{{#tag:ref
|AAAA link to B<ref name="expl_B" group="n" />
|group="n"|name="expl_A"}}
</references>
===References section===
<references />

Result: Failure. For one, it will twice generate an inappropriate <ref> tag with name "expl_B" defined in <references> is not used in prior text. (changing the order of the two #tag:refs makes no difference) Secondly, the <ref name="expl_B" group="n" /> is ignored. If however the "expl_A" is moved into the article text, everything is just fine.