Hey there! Sorry for late reply- to be honest I'm not sure what the technical term is. I've just been calling it randomly generated dialog, but I've heard others say it's procedurally generally (not sure if that's true or what constitutes as procedural lol).
Basically I just have a list of possible options and I pick one with equal probability. If you download the game and extract the files on your local machine you can actually see how it looks inside story.json.
Let me know if you find the proper term for it, I'd love to know myself too!