10 divisions per revolution is very coarse for encoder counts. Normally, there would be about 250 counts per rev. or more. The motors used with Gecko 320-series drives don't have steps; those drives are used with brushed servo motors. So it wouldn't be microstepping - are you sure the encoders don't have 512 lines on them? (You can usually open the covers and peek without damaging anything.) Servo motors typically have a bunch of skinny wires going to the encoders, but only two fat ones that run them. Steppers will have 4, 6 or 8 wires driving them, but encoders aren't often used.