That is interesting. We maybe should then ask the editors/publisher of the journal for clarification. Do you have any direct contact there? This could take some time. If you just need the issue thing, then replace in the locators macro the following:

<macro name="locators">
<choose>
<if type="article-journal">
<choose>
<if variable="volume">
<group delimiter=" ">
<text variable="volume" prefix=" "/>
<group prefix="(" suffix=")">
<choose>
<if variable="issue">
<text variable="issue"/>
</if>
<else>
<date variable="issued">
<date-part name="month"/>
</date>
</else>
</choose>
</group>
</group>
</if>

I will make the contribution for the official repository later, when it is clear how it should exactly look like.

I appreciate your efforts.
Thanks