This is in fact one of my two requirements when interviewing: I want to hear the candidate say "I don't know" to a question. The other is that I want to hear them talk passionately about some project they once did. Bullshitting is an immediate fail.
Each time I've gotten my way it turned out to be a great decision. When I've acquiesce to "but they knew all my java trivia questions" it's been a bad choice.
It's hard in the moment, but we'd do well to appreciate that not passing a myopic screen is likely a blessing.