Having been on the interviewer side of the table at a couple smaller companies as well as a FAANG or two, I can say I've never seen a question on the slate where the candidate was obviously intended to fail. Maybe some other companies do this.

However, if a candidate answers my first question easily I will try to extend or constrain the problem enough that it pushes them out of their comfort zone a bit. This gives them a chance to show off more skill than if I only asked an easy question.

Also, there are very rarely "perfect interviews"; it's rare for people to get the highest score on even one of their interviews, let alone all of them.