stikpusher:
FYI, be careful using that 1/6 item as a hard reference. I am unaware of the M2 .50 cal ever using a cloth belt. All that I have ever seen or used had a disintigrating metal link belt. The WWII Browning .30 cal used a cloth belt.
FYI at the beginning of the war the ground troops were being issued .50 cal ammo with "cloth" belts.
But the Aircraft magazines were not designed for the use of cloth belts, so as the demand for .50 ammo for aircraft weapons started to "increase", production concentrated more and more on ammo for planes. As this steadily increased, ground troops started to get a mix of Belted and Linked ammo, which of course eventually replaced the belted ammo altogether.
It was just plain econonmics, the cost of producing both belted and linked ammo, the cost of producing the containers for both (clearly marked), because you can't have belted ammo going to fighter squadrons. It was just cheaper to produce "one" type., and that ammo was needed at the front as quickly as possible.