The thing is that most of the merit badge work is not suitable for a notebook. The G2A clearly says that “discuss” means to participate in a discussion. Very few requirements involve making notes on paper.
For that matter, I think the whole merit badge class thing has been a major loss for scouts. Cringing at the “back in my day” thing, most of my badges the benefit was in the combination of doing and direct interaction with the instructor. A notable exception would be my Citizenship classes which met in a judges private chambers over the course of a couple months. But even there, a good bit came because that judge got to know me. I gave my letter to a congressman to him and he sent it off after looking it over. And he didn’t “grade” it, just. ensured I had met the requirement.