The location of the screws are important and my guess they are adjusted for every watch for accurate timekeeping.
The screws on the balance wheel serve two functions:
1) poise balance the wheel so it is not heavier in one position than another. This reduces positional variations of timekeeping.
2) the screws are part of the thermal compensation system. The hairspring elasticity varies with temperature so timekeeping also varies with temperature. A compensating balance wheel is cut at the rim near center arm and is bimetallic to aid in reducing the effect of temperature on timekeeping. When the temperature increases the wheel deforms to bring the free ends closer to the center and reduces its moment of inertia. This effect is more pronounced at the free ends of the rim. Having the screws located close to the center arm lowers the temperature compensation, having the screws located away from the center arms increases the temperature compensation.
View attachment 762075
From Hans Jendritzski, Watch Adjustment.
Click to expand...