This specific type of shelter happens to be based on ISO container specifications
"ISO 1496/1, ANSI MH5.1,5.1.1,5.4 (MIL-M-81957[AS],
In fact, some of the dimensions and tolerances listed on that drawing do NOT meet the ISO limits . . . The seem to have a mixed inch-metric system wherein they use hard conversions in some places and soft conversions in others, and this has led to some errors. They are small, but non-compliant, and are exactly the type of deviations that would cause me to reject the design if it came across my desk at work.
The difference with shelters I was referring to relates to the fork-lift pockets. Because shelters use different materials they have slightly different structures, and the pocket construction is different. The arrangement of structural members can cause the pockets to be in slightly different places, too.