I tried some more and while "numlockx on/off" does not change the LED in any way, it does indeed toggle the numpad on and off.
The numlock key itself toggles both the LED and the function of the numpad.
So, when starting with a computer that has the LED in sync with the real state of the numpad which for this example we assume to be "on", then "numlockx off" will turn off the numpad but leave the LED on. The LED and the numpad function are now out of sync. Pressing the numlock key turns off the LED, but switches the numpad back on.
I tried some more and while "numlockx on/off" does not change the LED in any way, it does indeed toggle the numpad on and off.
The numlock key itself toggles both the LED and the function of the numpad.
So, when starting with a computer that has the LED in sync with the real state of the numpad which for this example we assume to be "on", then "numlockx off" will turn off the numpad but leave the LED on. The LED and the numpad function are now out of sync. Pressing the numlock key turns off the LED, but switches the numpad back on.