I think there is a misunderstanding of what the judge has done here. She has sentenced him for 3 years for the rape but has additionally imposed an Order for Lifelong Restriction (OLR). The OLR is defined as:
The Order for Lifelong Restriction (OLR) is a unique sentence. It is not imposed for the crime committed but for the risk that the individual is assessed to present to the public. It is only imposed following conviction, and only after the preparation of a detailed Risk Assessment Report (RAR) can it be considered by a Judge in the High Court.
The OLR is a true lifelong sentence, meaning that all individuals sentenced to an OLR will be the subject of a Risk Management Plan (RMP) for the rest of their life.
What this means is not that he will be free after the initial 3 year sentence but that he will not be freed until he is deemed no longer a risk (likely to be 10-20 years) and that he will forever be subject thereafter to management which could see him re-imprisoned for any future transgressions.