Calling Uomi "Tsuda's official wife" quickly got picked up by certain fans after some untranslated strips revealed that she'd decided to use their relatives getting married as an excuse to get closer to Takatoshi through First-Name Basis and making food for him. Not to mention that she once "jokingly" tried to get him to sign a marriage license in the third second season OVA.
Many fans have also taken the "Flag-Crusher" nickname Uomi gave Tsuda and ran with it, especially since he has many, many Oblivious to Love moments with most of the girls.
Consider the following: Explanation Imageboards tend to use an image of Shino with those words as a reaction-pic. (It's a sub-mutation of a nearly identical Bill Nye meme)