It's happening with all the global groups with wikisets. The link doesn't point to the wikiset number.

In Special:WikiSets:

$set = is_numeric( $subpage ) ? WikiSet::newFromId( $subpage ) : WikiSet::newFromName( $subpage );

So both links *should* work, it's unclear why it isn't working.

Unsure if this is related, but I'm noticing that the value of $subpage is (I think) 'Opted-out_of_global_sysop_wikis', but it's stored in the database as 'Opted-out of global sysop wikis'.

Yep. I think we just need to pass $subpage through Title::newFromText( $subpage )->getPrefixedText() ?

The easiest way to work around this is to make it link to the wikiset ID instead of name. That's what Special:Wikisets also does.

But that doesn't solve the underlying issue.

In T61707#952982, @Krenair wrote:

But that doesn't solve the underlying issue.

as I said in the previous comment, it's just a workaround.

<Glaisher> eh.. that's totally weird.. phabricator's conflict handling
<Glaisher> I received a mail from gerritbot
<Glaisher> but it's not visible on the task

https://gerrit.wikimedia.org/r/#/c/182560/

Change 182560 had a related patch set uploaded (by Glaisher):
Link to wikiset ID on Special:GlobalGroupPermissions

https://gerrit.wikimedia.org/r/182560

Patch-For-Review