Hi, @amodeo, welcome to OGS!
As experience has shown with more than a year of using this system, the overall rank is the most representative of a player’s rank. Moreover, right now the developers are working on changing the way ranks are shown, and the overall rank is going to be the only one used in these calculations.
In an ideal world, you are right. But in practise, most of the users don’t play every time control. So you’ll see that most folks have only one rank that is following his/her overall rank in a quick pace, and the other two get stuck near their initial rank (most of the times 25k). This is why we mods need to constantly update those ranks when we find them, and this mostly happens when they are reported, so we usually fix it one or two games late. Fortunately, with the avobe mentioned rank update we won’t need to do this anymore. 