From this comment in SERVER-88502:

The testing for replica set endpoint so far has depended on duplicating a selected range of existing replica set and sharded passthrough suites but with replica set endpoint enabled, namely jscore, change_streams, jstestfuzz and concurrency suites. Those passthrough suites have helped uncover various feature parity issues between replica set and a sharded cluster with replica set endpoint enabled, but that's still far from complete since there are many features that tested only in non-passthrough suites: For example:

• Backup and live import, which are only tested in no_passthrough suite
• Auth, which is only tested in auth, ocsp, ssl, ldap and ese suites  

For this reason, we need to add a build variant that runs these non-passthrough suites by doing the following:

• If the test uses ReplicaSetTest or MongoRunner.runMongod (standalone), enable featureFlagAllMongodsAreSharded, featureFlagReplicaSetEndpoint like here and here so the replica set gets bootstrapped as a single-shard cluster with replica set endpoint.
• If the test uses ShardingTest and the cluster has only one shard, set st.s to a direct connection to shard0's primary.