Do you have any idea how many 30 minute shows I've watched where they have frequent multi-part episodes? The format is a limitation that people often circumvent with serialization of the story, which is expressly prohibited by Guideline #1.
Also, economy and efficiency don't necessarily make a story better. Ever seen Samurai Jack? Episodes often feature long pauses or beats for dramatic effect. The show only has 30 minute episodes, so they could do more elaborate stories if they removed those pauses, but if they did, it would actually undermine the dramatic pacing of the show.