That would be true if the condenser's efficiency was constant but it is not. It is less efficient during the heat of the day. On a split unit, the efficiency of the condenser is greater when the inside of the house is hotter and the outside is cooler because more heat can be removed from a compressed gas when the temperature difference between the condenser coil and the air passing through it is greater. Then you also have to factor wasted energy due to the compression equalization. When a compressor starts up, it has to build head pressure for the first few minutes on the high side before it can do anything. That is wasted energy. When the compressor shuts off, the high and low side equalize. It has to equalize or the compressor would never be able to start again. It actually takes more electricity to run an air conditioner that keeps cycling on and off than it does to run one that is perfectly sized to run nearly all the time. When you reduce the cycles, efficiency increases. Your block of ice analogy, while funny, is flawed.
Also, as a A/C repairman for many years, when you clamp an amp probe around the compressor load wire, you can see that it draws more amps during the heat of the day than it does when it is cooler. This is because it is less efficient when the compressor runs hot. When we recharge a compressor or check for proper charge, we use an amp probe, but we always have to take into account the outside temperature because it draws more amps (less efficient) during the heat of the day even though the BTU output is the same. We actually have charts that help us account for the drop in efficiency when measuring for the proper charge.
Put simply, the fewer cycles during the heat of the day, the better. You want maximum benefit? Turn it off between 9am and 10 pm then turn it down to 50 through the night so you have 1 cycle per day. While extreme and not very comfortable, that is where you would see the maximum benefit, not only to energy costs but also to wear on the a/c.