I tend to think of it as like two pilots as on commercial airliners: you always have one pilot flying and one pilot monitoring.

You can debate with agentic coding who is monitoring and who is flying but, if we assume the user is monitoring what that means, in practice, for me is that I'm reading and making sure I understand all the changes the agent is proposing to make, as well as providing instruction, guidance, correction, etc. That includes reading and understanding all the code changes.