EpisparhIt is a common design. You bring N amount of magazines during a fight. In reality you try to switch magazines as faster you can and collect them later when the things settle.
Have you ever loaded a magazine of a weapon? And then how you actually imagine extracting 1/3th of the plasma in one magazine to add it to another one?
It is natural way of thinking, this is why all games follow that approach.
Not sure why this is problem for you. Free unlimited ammo crates are literally everywhere.
I started on Lee-Enfields, 'nuff said.
I wonder how the Stowed Reloading mod will work then. Does it auto-bin your existing half-full mag and load a new one (annoyingly wasteful), or magically fill it back up (unrealistic). If the latter then you just got unlimited ammo.
If they just used a simple you have 300 ammo and have to reload after 30 or less shots then there would be no wastage and stowed reloading would be simple to implement.