I wanted to say something about how no matter how good computers are at understanding what humans mean, humans are still consistently bad at meaning they want. And something something, leaky abstraction something (... I didn't fully format that argument in my head). But it's already mentionned in the linked discussion.
Although, I don't see any reason why sufficiently advanced graphical programming wouldn't be able to match written code. It would require graphical elements that are more abstract and precise though, which would need to be understood. Technically what "codeless" is actually implying is "learnless" or "little learning required", which is where the actual roadblock is.