If time is feasible, I would suggest OP to book a HKG-TPE roundtrip / turn the JNB-HKG into JNB-HKG-TPE (depending on the rebooking fee and stopover rule) and remove the marcopolo number from JNB-HKG segment such that only the HKG-TPE RT segment will get credited within this membership year. Claim the JNB-HKG segment back later.