The Shutter-Beam interfaces with any set of studio or camera mounted strobe units via an standard PC jack output. When triggered the Shutter-Beam can directly fire your strobes hooked up to this output. Strobes have negligible propagation delay.
Strobes can have much faster effective shutter speed.
When the Shutter-Beam detects the subject it fires the strobes directly. The cameras film is exposed by the flash and then the shutter is closed and film advanced for the next shot. When in a darkened studio your strobe becomes the shutter. Strobes can be fired at a much faster shutter speed than your cameras shutter. The average every day camera mounted and studio strobes are not as fast as a millionth of a second.