alt Hacker News> The thing about subject matter experts is that they’re so good at their subject, they often aren’t aware of what they know.
It isn't quite the same thing, but "tacit knowledge"[1] is similar to this concept.
The difference is that the author is talking about things you don't know you know, where tacit knowledge is for things you know that you may have self-awareness but have difficulty conveying.
My favorite example of tacit knowledge is knife sharpening. Even with hundreds of 4k videos of it on YouTube, it's still very hard to teach because so much of the skill rests on the sense of pressure while you're sharpening, which can't be conveyed in video.