I am the maintainer of the CSL style "http://www.zotero.org/styles/norsk-henvisningsstandard-for-rettsvitenskapelige-tekster"

When citing treaties (type=treaty) I include the parties for bilateral or plurilateral treaties with the following code:

<names variable="author">
<name delimiter-precedes-last="never" name-as-sort-order="first" et-al-min="99" and="text"/>
<et-al term="and others"/>
</names>


For some reason, however, the "delimiter-precedes-last" setting to never does not seem to be respected. Here is a sample output (author names within the parenthesis, i.e.: Norge, Danmark, og Island):
Avtale om opprettelse av Nordisk Patentinstitutt, 5. juli 2006 (traktat mellom Norge, Danmark, og Island, i kraft 28. desember 2007) Overenskomster med fremmede stater 2011, s. 507.

For other item types delimiter-precedes-last="never" is respected, so that there is no comma before "og".

See, for example, this output:
Dystland, Marthe Kristine Fjeld, Ida Sørebø og Fredrik Bøckman Finstad, «Article 7 [Binding effect and implementation of EU legal acts]», i Agreement on the European Economic Area: A Commentary, Finn Arnesen et al. (red.), Nomos 2018. DOI: https://doi.org/10.5771/9783845275796-248.

The relevant code for that output is:

<names variable="author">
<name delimiter-precedes-last="never" name-as-sort-order="first" and="text"/>
<et-al term="and others"/>
<substitute>
<text macro="editor"/>
</substitute>
</names>


Is there anything I am missing here? Is there some typo or error in my treaty code that I am just not seeing? Or have I stumbled upon a strange bug in Zotero, CSL or citeproc-js?