I do find this set up a bit odd. A DMR is pointless without an optical sight. So from this I would deduce that the pictured weapon is either a DMR without an optic because the soldiers are on exercise or a march and didn't outfit their equipment fully (which doesn't make much sense either) or the weapon is the IAR.
The problem here is that IARs and other magazine fed squad automatic weapons (i.e M27 IAR, L86 LSW, QBB-95, RPK) cannot fully match the volume or sustained fire capability afforded by a belt fed LMG or GPMG. The benefit an IAR or magazine fed squad automatic weapon brings to the table is the capability to put down more precise suppression than can be easily afforded by a LMG or GPMG, but also more volume of and sustained rate of fire than a standard rifle but less than an LMG and GPMG (with bipod and heavy barrel) as well as ammunition and magazine compatibility.
To effectively use an magazine fed SAW concept as per my description above, a magnified optic is somewhat necessary. Even an unmagnified optic would be a large improvement for quick target acquisition, to get rounds down on the enemy as soon as possible.
Furthermore, if the optics aren't being used regularly, the whole QBZ 191 series of weapons is being ineffectively utilised. The 191 series has much greater accuracy than previous generations of Chinese small arms, this is exacerbated by the fact that these flip up iron sights are as they are designed, back up sights. They will not provide the level of accuracy or durability required for full-time combat use that may be afforded by built in iron sights that are designed for regular use.