Having done this prep, I can't tell if this comment is sarcasm. Building real systems makes you a good engineer. Maintaining systems over a long period of time makes you a good engineer. Working with other experienced engineers makes you a good engineer.

Doing this prep you do learn a few things along the way, but it's contrived. You already know what you need to learn, which is often the hard part on the job. It's works as a filter since the ability to learn concepts is important, but it's usefulness continues to trend downwards as it becomes more standardized.