This had a very narrow context - so you're right to push back on parent applying it generally. But Martin was originally saying that a program with DI will not

This had a very narrow context - so you're right to push back on parent applying it generally. But Martin was originally saying that a program with DI will not be as fast as a program without DI ... i.e., interfaces! When was the last time you were writing a program and thought that putting a class behind an interface would slow things down too much?