Let's assume, as you mentioned, that the person does not register and secretly communicates with a public office holder. There may be a complaint, perhaps a whistle-blower, and the commissioner will intervene. However, the fact remains that, if the public office holder was registered and reported the activity and the other person was not registered, it would trigger an alert. That would indicate that something was going on and that it might be worth investigating, even in the absence of a complaint or whistle-blower.
On May 30th, 2024. See this statement in context.