It's just one of those endings that kinda ... end, petering out, instead of elevating the story at its conclusion. It didn't necessarily have to be a confession, but to me there really needed to be something that made it clear that this wasn't just some chapters that also could have happened 10 or 20 chapters earlier and the story just continuing from there on.
For example, when Miss Sunflower asks Matsuri for her signature confession, so to speak, Matsuri could have said the next time she'd be saying it would be after hearing it back from Miss Sunflower. I'd have taken that ^^