Buzzbox beat me to it, he is correct. The difference between HKG and other ATCCs is that they will take into account the low local QNH and simply not assign a low FL that would create a loss of vertical separation. All transparent to flight crew and with less risk.
I can just imagine a situation in HKG with a weak typhoon, low QNHs, saturated airspace and a few non-local crew missing that little gem of a note.