My response is quite simply disappointment that this still counts as an interesting observation. It shouldn't. It shouldn't be anywhere near the category of things that one learns after teaching for years. On the contrary, it should be a first-order principle of teaching: It's fine not to know. The most dangerous assumption about teaching is that a teacher knows, and students do not.
A couple of times a year I work with high school teachers, and it always amazes me how quick they are to jump in and fill the uncomfortable silences and moments of student exchange that I try to craft with my pedagogy. Once the tension gets to the point of simmering, the high school teacher breaks the tension with a cool, refreshing dose of "here's how it is" which the students gleefully write down, happy to once again be deposited with valuable information. The script is familiar and comfortable. The students and teacher experience pleasure by filling out these roles. But is it teaching? Is learning happening? Unfortunately, it is, and it is teaching some dangerous assumptions.
I am always a bit surprised that the high school teacher is not immune, or does not celebrate the moment where the students are adrift and questioning one another. I too, participate in these moments, explaining that I am uncertain as well about them, and perhaps we should investigate further. I feel this is the best way to teach students that the solution to their recognized gaps in knowledge is not to guess, not to depend on an authority figure (which is pretty much all a high school teacher is these days), but to make a plan to address the lack of knowledge and shore it up as best they can for their purposes. Usually, this is the purpose of trying to sway an audience on an issue, one way or another, since I'm mostly teaching debate.
I think the reason that the above article is still interesting and a bit surprising, and the reason that high school teachers can't help but jump into and disrupt productive silences with banking-model discourse is because the trope governing the reality behind both is the same. That trope is that knowledge is at the root of authority. By this logic, the teacher risks losing all authority and control of the classroom if he or she is not the source of knowledge.
This is present in the rhetoric of the Chronicle essay as well. Discomfort at presenting a professorial subject that is not complete, or that is fragmented in some way is to risk upending the entire value of the course. It seems equally reasonable that a course in anything would teach you how to find out about it, not just information about it. Why does this trope hold so much power?
One reason might be that it dovetails nicely with capitalist narratives and capitalist desire. When someone is in a relationship in capitalism, the exchange must be even, or even for those involved. Not providing the right answer to a student question, or suggesting that you don't know the answer to a student's question is a very uncomfortable response in an exchange-system rhetoric. Not being able to provide what the customer wants is a terrible mistake, and can cost you everything.
The alternative trope is one where authority in the classroom, or perhaps the more soft version of the word for professors - quality in the classroom - is connected to the professor's ability to manage questions or the art of questioning. For this is the life-blood of the university, not providing an exchangeable service. The university should be equally preparing people for career and civic life - a life where the answers are not forthcoming, and we are generally operating on a best-guess basis. Those who can sift through the questions, reframe them, and suggest directions for answers are of the most value to society.
Training young people that older people will come along and spout out the unsatisfying, yet appropriate answer to everything is not the way to prepare people for a functioning society of any kind. What the author of the Chronicle piece has as her conclusion - that a student confronted with a professor who willingly admits she does not know the answers can inform career and life choices - should be the introduction to the preparation of future faculty and teachers for the classroom.