That’s fair, but also very clunky in practice, and essentially should be an implied point by anybody else who “knows C++.” It would be very clunky and annoying

That’s fair, but also very clunky in practice, and essentially should be an implied point by anybody else who “knows C++.” It would be very clunky and annoying to write on a resume “knows C++20 except have limited knowledge of exceptions, template metaprogramming, and default linker/make tools” when you can just caveat out all your blind spots when you actually get to talking about which parts you know (and when your resume is being reviewed first by nontechnical folks who will interpret carves like this negatively due to ignorance). It’s not wrong or misleading to claim you are eg a cancer researcher or study English literature while not knowing all cancer research topics or all works from all niches of English literature. Because everybody who works in those areas knows that it’s implied you were exposed to only a limited subset. If laypeople assume that “knowing” a broad and complex thing means you have 100% of knowledge across the entire domain, that’s a problem with their interpretation of the claim.