I think some of my confusion here was related to some notable youtubers misusing the term to mean a roll-on-heading exercise. When I wrote my last question, I was thinking "there's too much, or an unpredictable amount of adverse yaw", but I now understand the problem as "the aircraft enters a self-reinforcing oscillation in response to certain poorly coordinated control inputs", which doesn't sound like a good thing at all.

Thanks for all your input in this discussion. I find both flight in general and the case of the 737 MAX fascinating. Previously the implementation of MCAS sounded absolutely insane to me, but I can mostly understand how they got there after reading your comments.