Override Terms code in COM

To all,
Here is the scenario my customer has:  When they offer a promotion, they 
sometimes (as a part of the promo) give a 30 day extension to the customer's 
terms.  Here is the problem - when you override the terms from 30 days to 60 
days, COM handles it like this:
    1)    Changes the Terms code in the Open Order files
    2)    When it gets shipped/invoiced, the printed Invoice states the new 
terms description, the MBF9REP record has the new Net Due Days BUT
    3)    The printed invoice only uses the Customer Master terms days to 
calculate the Net Due Date which gets passed to AR.
    4)    Now the Credit person sees from AR reports and Inquiries that the 
invoice is past due when it really is not.

MAPICS states "that is the way it has always been" and that I should either use 
the Closings Before Current flag or key in the Invoice Date on the Order.  

Does anyone else run into this "design flaw"?  Why give us the ability of 
overriding the Terms and not bother to use them except for printing the 
description.

TIA...
Eric