This generally seems like good advice, but it does veer occasionally towards suggesting ways to appear good at system design when actually the point of a system design interview is to show the interviewer how good at system design you actually are.
This is an important distinction because it is not necessarily the case that the only way to pass a system design interview is to come across as being brilliant at it. I will happily take on a developer who shows that they have some good system design instincts but lacks a mature approach to engineering decisionmaking (assuming their other interviews show that they seem teachable and they have the other prerequisite skills). Not every developer is going to be a lead system designer. The interview is to help us figure out what kind of developer you are.
This is an important distinction because it is not necessarily the case that the only way to pass a system design interview is to come across as being brilliant at it. I will happily take on a developer who shows that they have some good system design instincts but lacks a mature approach to engineering decisionmaking (assuming their other interviews show that they seem teachable and they have the other prerequisite skills). Not every developer is going to be a lead system designer. The interview is to help us figure out what kind of developer you are.