Green Baron 737, I do not know much about Zhuhai approach, but I could say in Beijing, we only use "on standard" rather than "non standard", we were trained to advise the pilot the altimeter change when need to make a change, for example, you are 1,200m climbing and I clear you to climb to 3,000 meters, if both based on QNH, then we do not tell you QNH again unless there is a change in the QNH, and if there is a change in the altimeter reference, we will tell you, for example, you are 1,200m QNH maintaining, I clear you toe 3,600m on standard, we will say climb and maintain 3,600m on standard.
I suggest you ask controller if it is "on standard" or "on QNH", then you will understand that well, and personally, I think it should be "on standard".