If what you say, DC0, was to be the case then basically any general could pick a random pack of soldiers and just adjust their baggage train for the enhanced movement speed, which is very well documented not to be the case. Quite the opposite, any time our sources refer to such instances we hear of the carefully picked selection of troops that were more disposed to carry out such missions due to their fighting style, physical condition, supreme training and experience and the level of trust that the general had in them. It is obvious that once the movement speed and the element of surprise were the factors, the assigned army detachment was not pulling behind its whole baggage train and they only had with them what was most necessary. That doesn't mean, however, that this detachment would be composed of the random soldiers.