There's a difference between being able to drive stick shift, and "fully understand"-ing how to drive stick shift. I would absolutely say that I can drive stic

There's a difference between being able to drive stick shift, and "fully understand"-ing how to drive stick shift. I would absolutely say that I can drive stick shift because I've proven it to examiners in multiple countries (not every country permits a license exchange sadly), but to "fully understand" something is (well) something of a higher bar so I would ask how high? to make sure I understand what it is they expect me to understand. There might be a nuance that you (or I!) hadn't considered, for example driving stick shift with an unsynchronised manual transmission, or shifting without clutching, or something else entirely, and the point of the "fully understand" qualifier might be to call attention to something like this. For example: Say I can implement paxos in my sleep, debug someone elses implementation, and I can even design and implement a new consensus algorithm based on paxos where I may satisfy requirements of parts in slightly different ways that are extremely domain-specific but may be beneficial from a performance/time/space/cost perspective. This is what someone might mean by "fully understand"-ing paxos, but making some changes to paxos may take time for me to convince myself it is correct (or incorrect!), or there might be parts I think are essential/important that aren't (in some situations), and so I would still be interested in learning something new. Who wouldn't? However, I don't have good experiences with people who say "there are only X people who fully understand Y so you should use Z" -- it's usually means they don't understand Y as well as they understand Z, and that's not what I want from an expert.