While adding let in CDRIVER-4198, I realized that bypassDocumentValidation is not present on mongoc_bulk_opts_t. This is a minor issue, as it only means the option cannot be expressed when calling mongoc_collection_create_bulk_operation_with_opts. It can still be set on the mongoc_bulk_operation_t struct using mongoc_bulk_operation_set_bypass_document_validation (as PHPC does, since it does not use the collection method at all).