Not true. I keep track of what promises I've made, and who I've backstabbed. The times I've gotten the "serious matter" message haven't been related to that.
It's possible I had another diplo minus, such as becoming friends with a City-State or finishing a Wonder that they wanted, but you can't promise not to do those things.
No, it is always something that you have control over, One other think you declare friendship with enemy of this nation why have friendship with them, or declare war on there friend or something similar.