That is what these two "agents" were doing.
They were programmed to write code to help them understand their environment. In their code writing, they started developing a "new" code that only they understood.
I doubt anything devious was implied or inferred from their actions, but humans were no longer able to monitor what was happening and being said.
That’s still doing what it is programmed to do. It isn’t doing anything that it wasn’t programmed to do. An unforeseen outcome is not AI if the program did exactly what it was programmed to do.