This is not universally good advice. An interview is an obstacle that takes a limited amount of time. It can only approximate someone's true skill set. One can

This is not universally good advice. An interview is an obstacle that takes a limited amount of time. It can only approximate someone's true skill set. One can oversell themselves based on their potential to learn and grow. For example, if someone is a junior and they designed a micro-service with a senior but have a solid grasp of the process, then it's fair that they claim that they designed a micro-service. They can read up on the relevant concepts, answer a few questions in the interview and get a very nice opportunity in a cool startup. If they can learn to do it fast enough to be productive, then both they and the company are happy. On the contrary, by underselling themselves or being accurate, they are more likely get a job at their current level of knowledge, which can limit their growth potential. Still, this can be a good idea if someone is already very experienced and doesn't want to spend a lot of energy to grow.