I wonder if Strelets is trying for flexibility in this set? The Serbian army that fought in the Balkan Wars and the first two years of World War I was dressed in the Sajakca cap and the distinctive Serbian uniforms, mostly armed with Russian-supplied weapons (Mosin-Nagants and Maxims). After the army's defeat in 1915 and its great retreat over the mountains through Albania, the survivors were in rags and had lost most of their weapons along the way. When the army was re-formed on Corfu with mostly French assistance, they were given French uniforms (along with the Adrian helmet) and French weaponry like the Chauchat and the Lebel. That was the look of the Serbian army that took part in the battles of 1917-18 on the Salonika Front and later as the army of Yugoslavia right through the war of 1941 against Germany and Italy.
So it looks like the set is designed to be useable for two different time periods and two different conflicts - the Balkan Wars and battles against the Austrians, Bulgarians and Germans in 1914-15 and then the later Salonika Front battles in 1917-18 with French uniforms and equipment. Hopefully there will be a good enough mixture of troop types and weapons that each part of the set is sufficient for each conflict.