For operations in a session to get causal consistency guarantees, readConcern "majority" or writeConcern "majority" must be used.

However, these are only configurable for transactions occurring within the session.
And drivers only require read/write concern be configured at the level of a collection/database/client.

A use-case would be to set read/write concern to "majority" so all operations within a session have all four causal consistency guarantees described in the MongoDB Manual documentation.

This may align with the decision to have causal consistency enabled by default (per SPEC-936). It could make it easier for users to have higher resiliency guarantees by default.