Can field short to ground fry alternater?

Close.
When the engine is running, the alternator is the power source. So most of the time the ignition terminal of the regulator should be around 14 Volts.
But this is why its worth measing the alternator's output voltage, and/or the votlage difference between the alternator output (Bat terminal) and the regulator input. Then there is no question as to the voltage the regulator should be seeing.

When the regulator input is lower than set point, the regulator allows a direct connection to the field terminal. The field terminal voltage should be virtually the same as the input voltage.

However as soon as the voltage on the ignition terminal rises, the regulator's points open forcing the electricity to go through a resistor.
When the votlage rises higher, that connection is opened and no power is available at the field terminal.
The hot trick would be to view it on scope.