I 100% agree with you, and have used the same technique. Showing juniors that you are also human and make mistakes allows them to be less anxious about learning and trying new things. It also helps to keep them from trying to hide their mistakes which can quickly lead to larger system issues.

Of course, you have to have a culture where making a mistake doesn't immediately lead to being let go or publicly reprimanded. I have definitely learned quite a few things about people and code by helping juniors work through bugs that may not have been so obvious (including occasionally finding bugs in 3rd party libraries).