It looks like we mistakenly closed T388762 without implementing it for Parsoid. We probably only need a single line to fix that:

$extApi->addTrackingCategory( 'cite-tracking-category-ref-details' );

See T372709 for inspiration.

Change #1266211 had a related patch set uploaded (by Svantje Lilienthal; author: Svantje Lilienthal):

[mediawiki/extensions/Cite@master] Added tracking category for subrefs to Parsoid

https://gerrit.wikimedia.org/r/1266211

Note for demo time: The current solution skips the category in rare edge-cases when the sub-ref has errors that lead to the sub-ref not being rendered as a sub-ref. Here is one example that's different in the two parsers:

<references>
<ref name="a" details="d">a</ref>
</references>

This is probably acceptable in real-world scenarios because this can only happen when there is an error. The page is tagged with the error category then.

Change #1268926 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):

[mediawiki/extensions/Cite@master] Don't set tracking category when details="" is empty

https://gerrit.wikimedia.org/r/1268926

Change #1266211 merged by jenkins-bot:

[mediawiki/extensions/Cite@master] Added tracking category for subrefs to Parsoid

https://gerrit.wikimedia.org/r/1266211