Using an electric oven, is it okay to reduce the temperature leaving the cheesecake inside as the oven cools down to 250?

Yes it is. That's exactly how it's done. The cake will continue baking as the oven cools down, and that's built in to the cooking time. The higher heat helps get the crust set so it won't get soggy, and encourages the eggs to puff so you get a rise. But you lower it so you don't overcook those edges before the center has had time to heat and set. The combo helps get the right texture.