The reason they are assuming P(E|D) = 100% is probably because they are only envisioning what one particular god would do, not the whole search space: they are asking “What would God do?” instead of “What would X percentage of the zillion possible gods in the search space do?” The hard part is getting them to realize that P(E|D) includes Zeus, Loki, and the FSM as well as Jehovah.
The reason they are assuming P(E|D) = 100% is probably because they are only envisioning what one particular god would do, not the whole search space: they are asking “What would God do?” instead of “What would X percentage of the zillion possible gods in the search space do?” The hard part is getting them to realize that P(E|D) includes Zeus, Loki, and the FSM as well as Jehovah.