They should because it usually says when you hover over their picture after they make peace "peace treaty with xxxx".I'm starting to question that they even have a 10turn treaty even when they make peace themselves.
Have been seeing AIs start plotting on the target they have made peace with two times the last month or so, when I went into preparation mode because I was sure that they had a peace treaty, but then they suprise me abit later by simply declaring on their target again.
Maybe it was just ceasefires? Do the AIs do that?