If the predictions are independent, then I agree with you. I can think of reason why they would not be independent (trying to account for non-random polling samples, for example).
Look at his EV histogram; 332 EVs had the highest probability of occurrence at nearly 20%. While there are other ways to get to 332, I'd imagine most of that percentage is from a map like last night. That's clearly not the partial probability of each state multiplied together.