Looking from the standpoint of the generator it does not matter if it's output current is used for lamps or charging batt or heatgrips or shunting. It thinks current is current no matter what it is used for. So if you consume less current due use of LED's this might rise same amount in shunting indeed.

This of course with a shunting type regulator only, things are different with series type regulator.

For example you have 6000 rpm's and with no load the generator makes e.g. 30 volts.

All numbers here are illustrative only!

With 5 amps drawn it makes e.g. 20 volts

with 10 amps drawn it makes our required 13 volts.

So from the standpoint of the generator it has to be delivering 10 amps to have the bike voltage 13 volts.

Now the generator doesn't mind how that 10 amps will be spend in the bike, charging batt, heat grips, lights, shunting..

Suppose all bike consumers together take 7 amps, then the shunting action of the shunt-regulator will shunt the remaining 3 amps.

If you change halogens to LEDS then for example the consumption drops to 6 amps instead of 7, then the shunting will rise from 3 to 4 amps, all to get to 10 amps in total again.

So as long as shunting is active, there's no electrical benefit for the generator with LEDS.

But when you have for example 2000 rpm's and the generator voltage drops due that,

the shunting action of the regulator might stop completely to keep the bike voltage as high as possible.

Now in these cases the lesser current consumption of the LEDS vs halogens will help in getting the voltage up.

Again, with series type regulator the whole picture differs.

This is how I understood the principles so far, if it is prone to correction I'm all ears.