Before SERVER-85770 changes, RouterServer was only added at MongoD in two situations:

• If we deploy a shard and gEmbeddedRouter is enabled and we pass a --routerPort.
• If gFeatureFlagAllMongodsAreSharded and gEmbeddedRouter are enabled.

New change_streams passthrough suites were running only enabling gFeatureFlagAllMongodsAreSharded, not gEmbeddedRouter. Thus, all those tests were validated with a ReplicaSet without having ClusterRole::RouterServer, possibly breaking some assumptions.

clusterRole = {ShardServer, ConfigServer}

Once SERVER-85770 was committed, it has made RouterServer not depend on the gEmbeddedRouter feature flag, and once gFeatureFlagAllMongodsAreSharded is enabled on those new suites, we will always have:

clusterRole = {ShardServer, RouterServer, ConfigServer}

With that, all new change streams suites with replica set endpoint are failing.