You're reading the documentation for an older, but still supported version (1.33.4).
For information on the latest version, please have a look at 1.33.5.

1.4.1 Version

The real-time external control version is managed according to the input/output data structure version. The input/output data structures change between software versions; backward compatibility is maintained by matching the I/O data version that the external controller was developed with.