Almost all are simply playing "programming trivia." They name an algorithm or a data structure, and then evaluate whether you can recite it from memory. That's it. There is no problem-solving element involved. It is purely a test of whether you can memorize and recite.

This requires a lot less effort on the part of the interviewer than the style you describe, and also bolsters their ego and makes them feel clever when they find a candidate who can't recite properly.