This is so true.
I remember one of my interviews that went well in the end. In the middle of the interview, they mentioned using Java and building web apps. At the time, I was a C++ developer with no web development experience.
I said: "I never did web development," and their response was, "You do know how to write source code, don't you?"
I said: "Of course I do, but..."
They cut me off with: "You will pick it up, don't worry about it."