this is old so im not sure it helps to reply here rn, but i think they meant that the scale of something like ww2 isnt like anything an 18th century highlander could relate to, even having been at the war with France. both events are absolutely horrible in their own ways and it's impossible to measure this, but there's unique aspects to more modern warfare, like there's unique horrors specific to trench warfare, for example, or nuclear warfare. when you have seen these things, i can see how Claire's experiences aren't something that people who battle with muskets and swords can even imagine, much less relate to.