Major - P3 skip, batch_size, limit, and fields never had any effect.
Of possible flags values, only NONE and SLAVE_OK make sense, and SLAVE_OK is superseded by read_prefs. TAILABLE causes an error the driver tries to set nToReturn to 0, which the server rejects for commands. Other flag values are sent to the server without effect.
mongoc_cursor_t *
mongoc_client_command (mongoc_client_t *client,
const char *db_name,
mongoc_query_flags_t flags,
uint32_t skip,
uint32_t limit,
uint32_t batch_size,
const bson_t *query,
const bson_t *fields,
const mongoc_read_prefs_t *read_prefs)