In https://phabricator.miraheze.org/T7973, I requested the enablement of several extensions for our wiki. Most of those were indeed enabled, but it seems that sv4 and sv6 were overlooked. It might have been caused by their similarity to sc4 and sc6 (which also needed to be enabled). I did comment this on T7973, but did not get a response. Hence why I am creating a new issue.
These are available in ManageWiki already. Although there is a misconfiguration with sv6 and sv7 which I will be fixing.