AI offering open border agreements without tech

I've had 2 games in the past few weeks where an AI civ will approach me with an Open Borders agreement offer, with both of us doing open borders... and neither of us has the tech for it.

I was kind of baffled, and so I declined and tried myself and it wouldn't allow me to offer them still.

How did you know the AI didn't have Civil Service?

Post a save?