the dispatchChanges.php maintenance script (resp the ChangeDispatcher class, after If5ea19) filters changes by whether a given client wiki is (a) subscribed(*) to the entity that was changed or (b) whether the change affects the sitelink to that client wiki. The second check appears to be broken (always returns false).

Note that currently, the isRelevantChange() check is ineffective, since the return value is checked against !== null, which is always true, since the method returns a boolean (see Ib6f733).

(*) Subscription is currently determined based on wb_items_per_site, but in future will be determined via wb_changes_subscription, see T66590.