I really think Hi-chan lied to buy our Haruhi time to get her marriage situation in order before she presents Ossan to her father. This manga has managed to avoid common josei tropes so far, let's hope it continues.
I am not even sure that he knows they are married. I think he thinks they are living together and dating or something. Has she even told anyone (except ex-crush) about the marriage part? Even bestie thinks that he's her boyfriend.
Soon as Jooin remembers the past they keep alluding to it's a wrap (▰˘◡˘▰)