We intentionally do not apply mongod options to last-stable nodes here. A result is that the "majority read concern off" variant does not pass --enableMajorityReadConcern:false to last-stable nodes in multiversion test. This means we do not have the multiversion coverage we expect. Also, some tests like oplog_rollover.js assume that the primary and secondary have the same setting of enableMajorityReadConcern.