I strongly disagree. That dude had the most devious smile when he overheard Haruhi. He is most definitely plotting something
I agree with Kuroneko. He knows that their marriage is something that her father will never accept/approve of so he's making that work in his favor.
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.
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.