Anyone who meets the conditions can withdraw early. The nature of your residence in Hong Kong is not related to any of the conditions except in that, should you be applying for early withdrawal on the grounds of preparing permanently to leave Hong Kong, it should be coming to an end. In the permanent migration scenario, you do need to show that you have the right to settle in another country (I used my passport), but your legal status in Hong Kong is not in question.
Your permanent residence status is not affected by your announcement of your planned permanent departure from Hong Kong. It may be affected, however, by an actual permanent (or significantly prolonged) absence from the city.