I think that you got some bad information, Army Museum or not. You keep saying "they" when refering to your source of info. Who are they? Who produced the variations...the manufacturer, depot personel, military research? The cloth looks like cotton as jute is course. The fibers are very fine when I view the image at 200%. The whole suspension is off center and NO chinstrap provosion. Museum people and people of authority can be VERY stupid but unfortunatly, people take them at their word, probably more so in Europe rather than the "Colonies". ALL the presidential candidates in the United States are a good example of stupid.
If you ever go back to the museum, ask to see examples, not the word of a curator. The opionions and prejudices of a well meaning curator can be just as false as a collectors opinion. The curator was not living 120 years ago. Unless he can produce some kind of example or period printed mandate for such a suspension, it is just his opinion pulled out of the air.