I believe only Rolex movements have Microstella balance wheels
You may be confusing truing screws, which are used on many balance wheels to true or balance/align the wheel, for Microstella screws. A Microstella balance does not have a regulator (the lever/pin atop the balance cock) to regulate the movement. In place of the regulator, the microstella balance has a set of star-shaped (Microstella) screws that can be adjusted -- in or out -- to advance/retard the balance's speed. Here are 2 types of Microstella wrenches used to adjust the Microstella screws (the top wrench is a bit more accurate, while the bottom wrench is easier to use)
By adjusting a pair of Microstella screws by small increments, you can fine-tune a Rolex movement by a second or so, which is a fairly difficult thing to do with a standard regulator. Of course, the trade-off is that a regulator is alot easier to use than tweaking tiny Microstella screws. But if accuracy is the goal (as it is with Rolex), then the extra effort required to properly tune a Microstella pays off in potentially better regulation.