I believe you are looking at old documentation. Some number of years ago, --run-script-before was enhanced to handle various errorlevel values so you can choose to continue the backup or cancel it, and you could select the job result: success, warning, error.
I think it was mentioned that --run-script-before-required wasn’t really needed any more after that enhancement.
Here is the thread where this enhancement was discussed: Improvements for --run-script-before/after options