I can't see any reason why it would matter unless some one was convinced that the way that the two sides "keyed" into eachother mattered. Maybe they were trying to describe having the nuts on the bottom so that if they fell off, the screw would still be in place as a pin. But, then again, maybe they were trying to describe a method such that the joint faced to the rear for protection.
About split boots, there are some that are being sold "without hardware" for cheap.
Can screws and collars from a failed stock yellow boot be also used with a split boot? Or are they not compatible?
The yellow boots(1 piece) do not use screws and are thinner making clamp re-use difficult.
I have had some clamps fit, but for the most part is is best to buy boots with all hardware, unless you are replacing an existing split boot