I agree, personally as a CS Student, I gave contributing to open source a shot and I felt like it really helped me a lot. Joining a project's slack, chatting with maintainers, developing features with docs and tests and code reviewing really makes you feel like you're an actual software engineer. It gave me quite the confidence boost that I can do this after years of internship rejections and never knowing what I was doing wrong.

I'd recommend it for someone/student who feels like their technically competent but never got the chance to work with an already built codebase and a team because it really puts you up to the test.