The is a moment where the comm plates will actually short each other out, where part of the energy that is produced by one web is charged into the proceding arm web. So to speak depending on rpm this gradually decreases to micro seconds.
The more poles the cleaner the wave form pulsing off the motor.
Also 3 pole modification or dual phase motors utilize a brush directly over the comm plate for every neutral degree movement, say it is a 23 degree motor so every 23 degrees the brush is centered over the comm plate and the brushes are set so that the comm plates never short, this allows for circuit manipulation of the motor for a electronic adjustible offset.
2 pole uses a degree offset adjustible by the endbell (mechanical) for the amount of double plate contact at the 2 poles, the more positive the more torque less RPM, the moter negative the less torque but higher RPMs