Some people (myself included) can bullshit through such questions pretty well even when we don't know the answers. It's a skill, a combination of reading body language for clues, being confidently vague in the right places and turning attention away from dangerous questions with charisma.

You learn it quickly when teachers do oral exams at university :)

Code doesn't lie, so I understand why people like to check candidates that way instead of relying on talk alone. I would just prefer if it wasn't a hit-or-miss test on what algorithms you memorized.