I think what he means is that in order for the iphone to know exactly how long the battery will last, and thus be able to show an accurate meter, the phone must be charged to full capacity, then allowed to discharge fully so the phone and battery know the true charge level.
I know that my 3G needed it. When I first got it, it discharged down to the warning and then proceeded to last many more hours on empty. When I recharged it, the meter was more accurate.