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.

"But this conversation did get me thinking about the topic of culturally transmitted software that contributes to human general intelligence. That software can be an *important* gear even if it's an algorithmically shallow part of the overall machinery. Removing a few simple gears that are 2% of a machine's mass can reduce the machine's performance by way more than 2%. Feral children would be the case in point." [1]