OUCH! This sounds pretty bad. I’m glad you were able to make progress here.
I think it’s like… hard won knowledge among several people in the community and not really documented well? That certainly could be improved. If you want to open an issue I’d open it against elm-test and then make noise in #testing on Slack to get feedback. This seems like something that will see movement if you are willing to drive it forward, but not a lot otherwise—writing a blog post might be a better use of your time!