Diplomacy is the way to go. Tell an IO they made a mistake and it all goes wrong. Best to somehow turn it around and blame yourself... like I'm so sorry I am stupid I didn't tell you about my 180 day DTV.
It's common for people to have an individual experience at immigration/ embassy/ bank and then assume that is the way things are universally ... but infact requirements are different from day to day, office to office and even individual staff will create different criteria.