Again missing the point. I've said I'm fine with how it played out. In fact, we know she isn't that loyal after either so how is it still 'increasing her perfection and best wife points' xd.
Back to the topic, MC is a miserable old man, he has been living with this memory for more of his life than not. He's only been back to a kid for a week, having this image of Cathrine, the perfect girl that will always do the right thing, showing her evidence on how Aden cheated, Cathrine despite the evidence to not even confront Aden about it. And MC can just brush it off without even mentioning anything regarding that?
MC is also a person that has only been remembering the bad things that happened, beside Cathrine, before becoming a kid again. So you can bet she is important to him