I don't know about any recent upgrades to the voltage regulators, but the current capacity of alternators was determined by the resistance of the internal wires, not the regulator. I don't think the regulator has a current limiting function - it regulates the output voltage only. The regulator can only supply the required output as long as its input voltage (alternator voltage - internal voltage drop) is high enough. Higher capacity required thicker wire and consequently lower resistance. It does not take much resistance to drop the available voltage when you are looking at currents around 100 Amps - just 0.01 Ohms per volt at 100 Amps). Any internal voltage drop reduces the voltage available to the regulator effectively limiting the current.