Benchmarking

Many established industries and companies employ benchmarking techniques to identify and use "best practices" for their industries. For starters, I am curious why every modular factory seems to have a different design rule for spacing between modules. Some set it at zero, some use 1-1/2 inches and so on. Do other builders ignore this design spacing when defining the dimensions of your foundations/sill plates? If yes, what dimension do you use? I always thought it would make sense to use a "shot pin" type concept as they use in the metal toolmaking industry. This would guarantee a set spacing. Some set crews try to get the spacing close to zero, some don't much care it seems.
Thoughts?