Added information about it to both man and help.
Change prepared in upstream:
https://github.com/upgrades-migrations/preupgrade-assistant/pull/219

preupgrade-assistant-2.3.3-1.el6:

The --riskcheck option now has detailed description, both in man page and --help text:

      --riskcheck           Return the highest reported level of risk or result
                            related to system upgrade. Run Preupgrade Assistant
                            first - assessment of the system needs to be performed
                            before using this option. When this option is used in
                            concert with --verbose option, summary of the risks
                            are printed to STDOUT. If the --verbose option is used
                            once, just HIGH and EXTREME risks are printed. If it
                            is used twice, all the risks are printed.
                            Return codes:
                            0 ... SLIGHT or MEDIUM risk or needs_inspection,
                            fixed, informational, not_applicable, not_selected,
                            not_checked or pass result.
                            1 ... HIGH risk or needs_action result.
                            2 ... EXTREME risk or error or fail result.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2017-0819.html