In days of old, gasoline was drawn from the tank by a mechanical fuel pump located at the front of the engine and fed under low pressure to the carb's float bowl, wherein it came through a small orafice controlled by a needle valve. From there it was drawn through a small orafice in the sidewall of the venturi, where it vaporized. Matter experiences a drop in temperature when expanded, and draws heat out of everything around it. In the old systems, there were places where the fluid was moved through orafices and expanded, chilling, and any water in the system could be frozen. In addition, the fuel lines could drain back into the tank, and since water drops to the bottom of gas, moisture could remain in the lines and freeze.
Modern fuel injected systems are operated under high pressures as totally filled, closed systems all the way from the gas pump to the injectors. And when the engine is shut off, the injectors all close, keeping the system secure. There is no blowing of fuel through needle valves and orafices, there's no opportunity for water to reside in the fuel lines (unless there's an injector leaking, the lines will stay full of fuel just like a drinking straw stays full of soda when you seal teh top with your finger). There's no real opportunity for icing.
And then there's the ethanol.
And I agree that adding additional isopropyl alcohol is a bad idea. There's even concerns with older cars about "bumping up to" 15% ethanol, just approved by the EPA as an automotive fuel, because of conserns for the seals.