The US army study was probably for tasks within the US army not all tasks generally.
I was in the British Army. We exercised with the US Army from time to time. At the time I was working in the tank engine powerpack replacement section. The packs were taken out of the tanks and swapped. We stripped them and replaced the broken components. Engines, geraboxes, transmissions, hydraulics, etc.
We watched the equivalent US resources. The UK Army is smaller, very choosy, will not take people who do not have the requisite knowledge and won't allow cross transfer to roles unless they show an aptitude for the job.
In the US army it was upside down. Extreme specialisation and also much lower expectations. Where we had one person stripping a pack, with all the knowledge and experience to do so, the US teams had up to 6. Different specialisations and one sergeant or above guiding and managing the team, providing the knowledge required.
At the time, in the 80's, the US Army was so big that it didn't matter if the 80% were adequate or less, because the 20% were so big, so good and so powerful that nobody wanted to take them on.
US Army studies have to be viewed with a level of knowledge about who they recruit and what they do with them after they do.
Trying to apply them to situations in India or China is at best hit and miss.