I guess the reason I always wanted to set it up for the audience before the opening of episode 3, was to improve the impact of a lot of Grievous' wheezy/coward behaviour. If I knew that was Maul, I'd think "he's doing pretty good for a dead man" instead of "who is this new, awkward character and why can't he be more bad-ass?"

The suggested way for Obi Wan to learn the Maul/Grievous connection is for Grievous' eyes to be shaded most of the movie and then revealed as Maul's when he and Obi Wan finally face off in close-ups. It's a very good spot because it's directed as the moment when "it gets personal"... except that there really isn't anything personal about it. This story change is, in part, to help add the element that would have made that fight totally work.