Rough offset command restriction

[AFROUZ3]

Would you describe what the red highlighted sentence means, Please?

http://www-01.ibm.com/support/docview.wss?uid=swg1HD48031

Problem summary


Scenario:
Deviation Analysis result is different depending on the value
of extrude.
.
EXPECTED RESULT:
To document the behaviour of Rough Offset with the HIdden
area concept.

Problem conclusion

THIS PROBLEM IS PERMANENT RESTRICTION IN CATIA
Additional Closure Information:
Incident Diagnosis:
The result of the deviation analysis differ when performed on
the rough offset.
.
Reason:
[highlight #CC0000]The Rough Offset command is not applicable to surfaces having
hidden areas in every direction.[/highlight]
If the rough offset is performed on such a surface, the
result may be unstable. This is a restriction.
.
A knowledge article is created to inform the user about the
behavior of the command.
Please refer the knowledge article "QA00000018192" in the
Knowledge base