> I mean actually going into depth about things like algorithmic complexity, memory usage
OK, I agree that's definitely something the candidate should be able to do. I'm just trying to point out to anyone reading that it won't be sufficient to explain an algorithm. You have to actually write code to solve a given problem. That's not the same as regurgitating code you remember from leetcode, so please don't think that. You have to apply techniques that you've learned. It's not easy, and it's not intellectually shallow.
As an interviewer (granted not at FAANG) I see no value in you just proving you did an algorithm on Leet Code. You could just be passing it through rote learning. I want to make sure you understand it. Otherwise I'm just wasting your time. But that's just my interview style, I know bigger companies may be different.