Some of the OOCness was intentional (like Sakura acting like her early part one self in the beginning).
There are a lot of ways to convey some meaning, some idea without making characters regress and act OOC. There is no such technique in literature - make your characters act OOC.
By doing exactly that the author is saying "I can't really write a story, only go back in time and repeat something I've already shown gradually in compressed time".
It is a disgrace for an author really.