You are giving an interview round where you ask 2 questions. The candidate fails the 1st one badly. Do you give an easier question or a harder question for the 2nd?
The answer is to give them a harder question. This is because your goal as the interviewer is to always seek out a path for the interviewee to get a pass.
For the Facebook onsite DSA round for example, you are generally required to solve 2 Leetcode Medium problems. If you bomb the first Medium, you are in a deep hole. Yes, giving them a Leetcode Easy gives them a better experience as they will probably be able to do it, but even if they give the best answer in the world to a Leetcode Easy, that is not enough to justify a pass on bombing a Medium. You are doing them candidate a disservice by essentially giving up on them.
This is why when I saw a candidate completely wipe out on my first problem for the Facebook DSA onsite round, I would follow up with a Leetcode Hard. This is because doing very well on a Leetcode Hard is enough to cancel out a bad performance on a Medium - I am giving the candidate a chance for survival. Sometimes a question just doesn't land well with a particular candidate or they need the 1st half of the interview to really get into it - Admittedly, this rarely happens, but again, my goal as the interviewer is to bring out the best in the candidate and hopefully get them into the company.
Anyways, I hope people like this additional insight from the Big Tech interviewer's perspective and would love to hear people's thoughts on this. It's a bit weird, because you could totally interpret getting a Leetcode Hard as the interviewer just being mean to you, but it's possible they're doing this because they are trying to save you!