Hmmmm the last time i playtested it the true ending can be obtained as long as you get six peaches, but I'll try to look at it again (hopefully i still have the raw codes) 🤔 do you get the ending with the explanation of kuon/koan first meeting (because that's the true ending)?
The same thing happened to me. I got all the peaches and dialogues but still got the normal ending where he just falls asleep upon returning home.
edit: i was just fooling around with some game-play options and i realized that i only got the normal ending when i replayed some of the peach scenes and then went home. when you don't replay the peach scenes it seems like you get the true ending. hope that helps!