The point the post makes is that one can’t write (or ensure that) a piece of code is correct without understanding it in the first place.

It’s most important, above these, because you cannot ensure any of these other design goals without understandability. It has to come first

And I agree with that. Correctness is the goal, but making the code readable is the way: it comes first. Cutting corners there is a good way to shoot yourself on the foot.