All the automatic or semi-automatic coil winders I've ever seen just relied on a turns counter for feedback and assuming normal tolerances of the bobbin size and wire gage, I would think it would turn out very repeatable induction values, and many of them turned out beautiful looking windings. One could always measure the final induction value and trim if needed. As far as creating a 'perfect' symmetrical magnetic field, I have no idea how critical or difficult that can be nor if wire gauge variation would have an effect, turns is turns.
Lefty