Not too sure about the case in the article and if relates exactly, but it made me think about spaced-reptition systems. I aim for a 80-90% success rate as I've found that to be the optimal range (arrived at that after doing this for 10+ years now with varying settings).

I found other articles about this: https://eshapard.github.io/anki/target-an-80-90-percent-succ... https://vladsperspective.wordpress.com/2017/03/14/optimize-y...