[N1QL Explain Plan] test_bidirectional_join fails: covers missing from explain plan of join query

This could be related to:
MB-25317 which is now closed, hence I did not reopen the issue.

Test failing:
./testrunner -i <ini file> -p doc-per-day=6 -p standard_buckets=1 -p primary_indx_type=GSI -t tuqquery.tuq_join.JoinTests.test_bidirectional_join

Query which fails:

explain SELECT meta(b1).id b1id, meta(b2).id b2id FROM default b1 JOIN default b2 ON KEY b2.docid FOR b1 WHERE meta(b1).id > ""'

Indexes created:
self.query = "CREATE INDEX ix1 ON default(docid,name)"
self.query = 'CREATE INDEX ix2 ON default(docid,name) where type = "wdoc"'
self.query = "CREATE INDEX ix3 ON default(altid, name, DISTINCT ARRAY p FOR p IN phones END)"
self.query = "create index idxbidirec on %s(join_day)" %self.buckets[0].name ;

Assert which fails:
self.assertTrue("covers" in str(actual_result))
https://github.com/couchbase/testrunner/blob/master/pytests/tuqquery/tuq_join.py#L132