The specification requires: "For both the collection-level and client-level bulkWrite() methods... Drivers MUST evaluate eligibility for each write command sent as part of the bulkWrite() (after order and batch splitting) individually." (this requirement predates the client-level bulkWrite). However, from the inception, MixedBulkWriteOperation has been evaluating eligibility only once, when creating the first batch via BulkWriteBatch.createBulkWriteBatch, and then reusing that result for all batches.

This means that a single WriteRequest that is not eligible for retries renders all commands executed by the operation non-retryable.