The RHO does not apply outside Hong Kong. Simply because a conviction is spent in Hong Kong does not mean it will be ignored by another jurisdiction. This is particularly relevant for applications for a travel visa or for immigration.
Criminal records are maintained by the Hong Kong Police Force. A person wishing to immigrate to another country will be asked to provide confirmation that they do not have any criminal convictions. That can be done only by obtaining a Certificate of No Conviction from the Hong Kong Police. If there are previous convictions, the Hong Kong Police will not provide a Certificate of No Conviction, however long ago the convictions were. The Hong Kong Police will refuse to issue a Certificate of No Conviction even though the conviction is spent in accordance with section 2 of the RHO.