The game is very obviously rushed, you can tell that for most of it the pace is quite slow, balancing the daily life stuff with the monster-killing stuff like in Persona but after a certain point during the summer you start rushing through all of the games' antagonists and the ending. The most evident hint is that when this starts, the date in the menu changes to "XX/XX", so they had the ending ready to slot in at any time. There were probably plans to include events with them but they ran out of time.