Correctness is binary even in context. The axis of which you speak shows distance; essentially how close the programs were to being correct. Every single sample was incorrect.

Think of it as being like a road trip. Arrival is binary. You have either arrived or have not arrived, but distance can tell you how close you are to arrival. Being almost there does not imply that you have arrived, however. Same applies here. Some samples were closer to being correct than others, but none were correct. They were all incorrect.

But as you alluded to earlier, I don't suppose anyone wants code that fails to solve the stated problem. Given that we have empirical evidence that LLMs cannot produce correct code within a given set of problems (and I suspect that extends to most problems), correctness is a weak signal.

What is a useful is to know is how much additional effort is required to make the program correct. That is what quality has traditionally meant as it pertains to code. High quality codebases are considered high quality because the effort to reach and maintain correctness is considered to be low. We do not have enough context to know for certain if that is what was meant in the earlier comment, but it seems likely. What we do know is that the comment is about quality while the article is about correctness.