Not all clubs react the same way on contact! The alignment line used by the manufacture isn’t always the centre of gravity of the putter face, casing the face to Open or Close. You always need to measure the effect of ball & club contact; it is very difficult to predict what will happen. Different styles of putter shaft, grip, even face rotation and grip pressure by the golfer themselves can affect the amount of face twist...
0.5cm out of the toe/heel has an effect on the ball’s start direction.
The greater the error in strike, the greater the effect on the ball’s start direction.
IMPORTANTLY, the effect of a toe/heel strike on the ball’s start direction varies between putters.
Impact Ratio – effect on Ball Speed?
How does clubface rotation affect club head twist, does it change depending on the speed of rotation?
High and Low impact location on the clubface also will give cause for concern, both in terms of launch angle of the ball and resultant ball speed!