On a three wire set up the alternator should go off line. The 2 or R term are the sense terminals, once it goes to zero it should shut down.
I do believe the very early 10si employed secondary regulation. It may really depend on the regulator. A generator of course a different story.
To simplify one's thinking take amperage out of the equation. The alternator cannot make any device take more amperage. The device determines this (voltage goes up, amperage goes down).
Think of your alternator as a wall plug. It will provide 14.25V at 70° with enough mechanical input. If rated at 60 amps it will provide what ever amperage the car (device) demands up to 60 amps.
The higher that amperage demands the lower the voltage, typically on an analog system the voltage will ramp down. That is to say a good 60 amp analog alternator may produce 40 amps at 13.5+V off idle.
Just to add to the discussion I rarely if ever use an amp meter when checking alternators or generators. If all the loads the car needs are satisfied there is no need to know amperage. On a modern car if all the loads are on and the battery is seeing 13.6V or better amperage becomes a moot point.
Hope this helps. Caveat, I have been stuck in the office for over 10 years so this is from memory, what ever that is..
