This is just one an example of the centuries long trend in modern military history of increasing dispersion in the face of increasing firepower.

Elite troops (i.e. Guard Regiments) in Napoleonic times were elite because they were better organized, braver, more disciplined and sometimes physically larger and more intimidating than other units. They could retain their unit cohesion under fire or when entering melee, where it would be decisive. Under Napoleonic conditions, the side with higher morale that sticks together no matter what usually can win an infantry slugfest.

In modern times, or even the 20th century, the conventional ideas of bravery and a "stand-up fight" have disappeared in the face of increased firepower. Under artillery, machine gun fire and aerial bombardment, troops can't outclass their opposition by being bigger, braver, and more tightly organized. Troops have to spread out, conceal their position and use dispersion to avoid being overwhelmed with firepower. Concentrated groups of elite troops would quickly become targets for firepower they can't even necessarily see. Similarly firepower of a large group of troops tends to depend more on the number of artillery tubes and machine guns a unit possesses, and the expertise of it's officers and specialists, rather than the abilities of individual soldiers.

However, with dispersion comes a whole different problem. How can units keep fighting and accomplishing objectives if they can't actually see each other or their chain of command? 20th and 21st century militaries have found various ways of training units to deal with this problem in standard military units.

Elite units in modern times go into situations where the utmost dispersion is required: At the tip of a fast moving armored column, suddenly appearing by aerial insertion, or infiltrating behind enemy lines or into a country where they can't operate out in the open due to politics. These situations are ones which are more chaotic than normal and where the additional dispersion might be expected to break down communication and inhibit military effectiveness.

In these situations, extra training is needed to make sure that the individual soldiers can fight under more chaotic than normal conditions. Soldiers need to use more individual initiative and be comfortable fighting in smaller groups and in more unexpected situations. Extreme physical training in modern elite troops is needed not to intimidate the enemy or overpower him but to provide the flexibility to hike over a mountain or into a jungle and still be combat effective when away from motorized logistics.

Napoleon's Imperial Guard was in thus "braver and brawnier" than regular troops. Whereas modern elite forces are "smarter, sneakier and more flexible" than their regular army counterparts, and the change is due to an increase in firepower and dispersion in the modern era.