It is not a matter of manufacturer that makes the difference but rather what the regulator was designed to do. It is mostly a matter of whether you are going to have low cut in speed or low parasitic draw.
The draw through the regulator is used to provide a small voltage through the brush and slip ring to the field coil in the rotor to provide enough magnetic lines of force to get the alternator to start charging. The lower the magnetic field the higher the RPMs need to be to generate enough voltage to start charging. The higher the voltage the more milliamps it draws but it also lowers the RPMs needed to get the alternator to start charging. Once the voltage produced by the stator exceeds the voltage that the regulator is providing to the rotor coil, the voltage in the rotor rises and in turn increases the output from the stator. It keeps increasing until the regulator takes over to control the output voltage.
The output from the diode trio is connected though the regulator to the number 1 terminal. That allows regulated voltage to be applied to the field coil instead of the just the small amount the the regulator passes though with the alternator at rest. That is why once the alternator starts to charge the RPMs can go quite low and the it will continue to charge.
Charging voltage is controlled by the regulator by grounding the other end of the field coil as it returns through the other brush and slip ring. When grounding the regulator tab through the D shaped hole in the back of the case you all taking the regulator out of the circuit and causing maximum current flow through the field coil in the rotor.
Voltage sensing to serve as a voltage control is usually done at the number 2 terminal but there are some regulators that have no connection at that terminal and use either the voltage provided by the diode trio or separate wire coming from the rectifier bridge. Those that use a separate wire will have a small stud to attach the added wire.
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