That reminds me of another fun fact about the press release, the episode 2 and 3 levels are swapped. E3M5 is E2M5 and E2M2 is E3M2. They were probably following the doom bible with the moonbase > hell > corrupted moonbase story. This could possibly explain why the spiderdemon has less health that the cyberdemon, because it was not intended to be the final boss.