Returning to this:
I tried Brad's suggestion of viewing by chapter on the grading page.
This does seem to be a good solution for viewing student responses and giving feedback.
The grades they get for the question on a corresponding assignment do not show, but this is ok.
However the recurring frustration is that students are trying to do *reading* assignments without ever doing any reading, and then complaining that they only got 5 out of 6, because to get the 6th point they had to at least open the correct section in the textbook!
I would switch to simply assigning a section with a minimum activity count, except:
(a) I don't think this is what the PROTEUS team wants us to do
(b) This would bring me back to an earlier problem: a section might have 10 activities, 5 of which are exercises, and 5 of which are videos.
I don't want the videos to count towards the activity count, but we currently don't have a way to avoid this for PreTeXt books