I just read the first page but he is wrong on this guess.
Now then. I am not quite sure about this, so I will have to confirm this with Theo, but my guess is this: the regulator/rectifier unit gives the battery what the battery wants, and REFUSES TO ACCEPT ANYTHING MORE THAN THAT FROM THE GENERATOR! This leaves our generator with the sudden unexpected task of sinking the excess energy into -- somewhere. Our poor stator has no choice than to sink this for a large part into its own coils.
Nope, the generator output is purely governed by rotational speed as the wire turns are constant as is the magnetic field of the rotor.
The reg/rec rectifies the ac voltage(about 60vac) to dc and the reg dumps excess power to ground when the battery gets to, in theory, 14.2v dc. This is very similar to the Zener diode system used on 70"s brit bikes