It works. Did the last 3 levels like this and my chievo popped.
It DOES also update your service record, saying you completed the extra levels and completed the game on legendary, and I got the Mark VI armour for War Games, too.
The only downside is that it won't give you the challenge for completing whatever level on solo legendary.
Last edited by Kamakazi Pear; 12-15-2012 at 05:37 PM.