But if you are training, this is the real configuration. Troops should be acclimated to carrying the belt box, spares, extra mags, etc. etc. I can understand doing a simple firing test, but I don’t think training in the way you described would be right.
The main point and purpose of an LMG is sustained automatic fire, ideally accurate sustained automatic fire. Even Rambo will struggle to achieve that latter firing from the shoulder or hip.
This is why LMG gunners almost always go prone or seek cover they can rest their LMGs on to fire.
For a low intensity patrol, it’s totally reasonable to use a 30rd box mag so the LMG gunner can immediately return fire in the event of unexpected contact as he seeks cover from which he could mount his gun and make sustained fires from.
Indeed, having that flexibility is one of the reasons for designing the LMG to be able to feed from magazines and belts.
The PLA do not mother their soldiers during training, and often go above and beyond, such as making soldiers maintaining aim for prolonged periods of time with hanging full water canteens off the battles of their rifles. So no need to worry they are going soft on training.