'Generate generator' command is missing in Drush 12.5+ (present in 13)

[rloos289]

Existing document
https://www.drush.org/12.x/generators/drush_generator/

What are you attempting to do
Use the listed drush generate drush:generator command

In what way is the existing documentation unclear or incomplete
The command doesn't work in drush 12, I get an error saying Command "drush:generator" is not defined.

What should the documentation say instead?
There should be a warning that it doesn't work by default. Maybe suggest users use Drush 13 or pin DCG to version 3.3