Missing gear vs secret sauce

I want to distinguish between the following two framings:

• missing gear/one wrong number problem/step function/understanding is discontinuous/payoff thresholds: "missing gear" doesn't imply that the last piece added is all that significant -- it just says that adding it caused a huge jump in capabilities.
• secret sauce for intelligence/small number of breakthroughs: "small number of breakthroughs" says that the last added piece must have been a significant piece (which is what a breakthrough is).

I'm not sure how different these two actually are. But when thinking about discontinuities, I've noticed that I am somewhat inconsistent about conflating these two and distinctly visualizing them.