I don't know of any organization that places that kind of time in grade requirement on a promotion for first to second. I don't even think Gracie Jiu Jitsu had that kind of requirement when they got the respect for having integrity in grading. Most schools that want to make their gradings "mean more" tend to stretch out the time in colored belts. I know some organizaitons require a time in grade equivalent to the dan grade you're going for, but that would still be only two years from first to second.
Integrity in grading isn't dependent upon time in grade but on clear communication as to what each grade represents and not promoting students who haven't met the standard. KKW grading requirements are fine, in and of themselves. The problems arise when the belt system is turned into a profit margin padding device and the black belt is inflated to mean more than the KKW makes it mean in order to justify an insane price tag, while students are being hurried through colored belts in order to grab as much money as quickly as possible.