IMHO less than one degree (strict) accuracy is needed. It's a bit similar when you set the basic ignition
advance by turning the dizzy, that also need to be very accurate to keep the actual ignition advance curve
to the design specifications as close as possible.
I think there might be an other limiting factor: the angular diameter of the teeth, and the gaps between them.
More precisely will the original crank senor be able to follow the weaker magnetic flux changes generated by the
smaller teeth/gaps? The sensor have electrical impedance, which limits the minimal flux change that it can convert to electrical pulses. (and I guess at some point the sensor output may drop beyond the operation
threshold of the control unit)
Somehow it would be nice to compare the output levels of the original and the new trigger rings...