Based on this comment
We might be able to remove this ugly call in ReconciliationService
// XXX: This bit is so annoying... $baseRevId = $this->entityRevisionLookup ->getLatestRevisionId( $base->getId() ) ->onConcreteRevision( function ( $revId ) { return $revId; } ) ->onRedirect( function () { throw new \RuntimeException(); } ) ->onNonexistentEntity( function () { throw new \RuntimeException(); } ) ->map();